Several members asked questions about the meaning of LEADGEN lately and since I couldn't find any guide here on STM that would explain it, I decided to write one ... and here it is 
There are many different types of offers that you can choose to promote in Affiliate Marketing. Some of them are more popular, some are less … some models are new, some have died already and then there are some that are around for ages and don't relate to ONLINE business only.
LeadGen is one of such models, or offer types. It has existed even before there was the internet and it's absolutely not going anywhere, even if electricity ceased to exist
It's simply one of the most popular customer acquisition models that has been proven times and times again … that's why you see LeadGen offers recommended as a safe vertical to enter, regardless of the current state of the Affiliate Marketing landscape.
SO WHAT EXACTLY IS LEADGEN, WHAT DOES IT MEAN?
Lead-Gen is a shortcut for Lead Generation – so it's the process of getting leads.
Leads are basically potential customers, who expressed their interest into a product, service, gift or whatever …. that either IS or IS NOT directly related to what we actually want to sell them … in either way, they gave you their consent to contact them with a follow up offer, or some advertisement.
Did I confuse you with the “IS or IS NOT” remark?
Let me explain it more.
In order to get contact information from someone, which basically turns them into a lead, you need to offer them something. They won't just approach you on their own and beg you to “spam” them with product offers 
So you can either offer them something that is directly related to the final product that you are selling : free limited access, free phone consultation, trial period … OR you can use a “lead magnet” like a free iphone, samsung tablet, shopping voucher … and then send them offers for whatever the hell you want.
More clear now? I'm sure it is.
There are several types of Lead-Gen offers, defined by the means of future communication with the customers.
The main types would be Email, Phone Calls or some sort of Membership site (or mobile app) that requires the creation of an account or other means of registrations. The latest one usually utilizes some kind of internal communication system too.
LET'S TAKE A CLOSER LOOK AT THE LEAD TYPES.
I outlined a few communication channels that are used in the Lead-Gen vertical, so let's talk a bit about each of them.
EMAIL LEADS : this is probably the most popular contact method used in the leadgen niche. The customers give you their email address, along with a permission to send them promotional emails. Email leads are often collected with the help of a lead-magnet that is not related to the actual product, that we want to sell our prospects.
All the sweepstake offers, free iphones, samsungs, shopping vouchers … all of these are email Lead-Gen offers that aim to get as much Leads as possible, so they can slam their email boxes of offers of all and any kinds 
On the contrary, there are offers in the BIZ-OPP or Education vertical, for example, that offer a free lesson, e-book or video tutorial in exchange for the email address … leads generated this way are more targeted and produce better results.
There are two terms that you need to understand here : SOI and DOI.
Single Opt In (SOI) lead : as soon as the prospect enters their email address into some collection box, it's considered a valid lead. No further confirmation is needed. The “system” usually does some general scan, so bogus emails won't get through.
Double Opt In (DOI) lead : once the prospect enters the email address into a collection box, the system sends them a verification email with a link that they have to click on. Once they clickit , the lead is considered valid. This is a form of verification to confirm the validity of an address as well as a legal requirement in order to be able to send emails to the prospects legally.
NOTE: Large part of GEOs require email confirmation – emailing to in-confirmed emails is considered SPAM. So pretty much any advertiser is doing this, SOI is pretty much just a payout option for affiliates.
SOI leads are always paid less for than DOI leads, simply because there is some fall-off form SOI to DOI, some people won't confirm and some emails are not working.
PHONE CALL / MAILING ADDRESS LEADS : This method is using the more traditional means of contacting our prospects. These are mostly using the “related to final product” approach.
The most used method would be asking for phone number, in order to have a sales agent or support person contact customers, with more details, custom calculation or a special offer. The call centers then to their job and try everything possible to close a sale.
In case of mailing address leads – there is usually some form asking for basic contact details, which is then used to send catalogs, discount coupons, fliers or other promo materials directly to the prospects. Another method that is used very often is asking for contact address to send custom quotes or personalized offers to customers who showed interest into a product or service
Typical examples of Call/Address leads would be : solar panel quotes, financial services (insurance), bank loans, catalog based products … even car price quotes etc … there is a ton of niches that work with this model.
MEMBERSHIP / REGISTRATION / APP DOWNLOAD : This is the last from the major lead-gen models that I want to write about, in this article.
To quickly illustrate how this method works, let me use what I think is the best example : DATING SITE. Users come to the website (or mobile app) and in order to see what is inside, they need to register and create an account. This is usually free, but gives them only limited access or limited functionality. Once they become paying members, all functions are unlocked and they can communicate with the other members freely.
The beauty of this approach is, that it actually combines 2 models – on one hand, the registered members regularly visit the website, which means they can be further monetized by ads or other up-sells. And at the same time, they had to enter their email address when registering, so they were actually converted into EMAIL Leads too.
Only a small % of the users will actually become paying members, so the large part of revenue for the advertisers comes from utilizing the email addresses. In many cases, they get resold to other advertisers, users will get co-registered to other sites at the same time … etc
As I mentioned at the beginning, these sites or apps pretty much always have some internal communication system in place. This is used to persuade free members (leads) to purchase a VIP membership, chat bots are often part of the process….
Dating is probably the best example I could use, but that doesn't mean there are no other “registration leads” offers available : pretty much all APP Installs fit this description too – utility apps, games … I've seen education/training programs that utilize membership zones too… there is a lot of variety here too.
Since this method is tied to email collection so closely, you will see that a large part of such offers actually uses the SOI or DOI conversion point to determine affiliate payouts.
THAT'S IT, ALL CLEAR I HOPE 
I think I explained the LEAD-GEN system pretty clearly, but in case you have more questions, fire away and ask them 
In case you're wondering what method you should focus on… SOI email leads are the easiest to get by far, so it's the perfect choice for a newbie affiliate. It's pretty easy to convert users into SOI leads, but it's also the least paying option and the most prone to quality problems.
That's why I recommend experienced affiliates to focus on DOI more. They are usually more stable too.
That's it, thanks for reading 