Other covered the basics pretty well, but as a Conversion Optimizer that specializes in Drip Marketing, I thought I'd add a few things.
Let's start with a concrete example: imagine you have a project management software and your goal is to get people to sign up for your free trial. From that free trial, your goal is, of course, to convert trial users into paid customers.
So it seems logical that your conversion goal is to get as many people as possible to sign up for the free trial. I mean, many SaaS companies will have a "Sign Up For A Trial" call-to-action button all over their website, and then they test and optimize to increase signups.
But in the majority of cases, that's a flawed approach, and that's why drip marketing is so important.
2 main problems with that "focus on the trial" approach:
1. Many people sign up for the trial simply to see what the software is capable of. They want to see if it's right for them and if they want to stick with it. In this case, churn usually goes up as most trial users never come back.
This happens all the time, and the biggest sign of this happening is when you start noticing your churn going up and conversions to paid accounts go down, even though trial conversions might stay the same or even increase.
That scenario is often due to unqualified visitors signing up, an unclear value proposition that forces people to sign up to figure out what you're about - and tons of other smaller things.
2. New users aren't being onboarded properly. Now let's say your site's unique value proposition (UVP) is clear, your sign up flow is optimized, and qualified visitors are signing up to your trial at a good rate. It's still possible that your churn increases.
Here, the root cause in almost all cases is due to a poor onboarding process: people signup, and then they're thrown into your software without being sure where to start. Even if they're your perfect customer, they might end up leaving and never coming back due to confusion or due to unwillingness to take the time to figure out how it works to use it efficiently.
So why am I telling you this? Because these are the top 2 problems Drip Marketing solves.
You see, the goal of a drip marketing strategy is to capture leads, and then nurture these leads through a series of emails.
This way, you're able to build a relationship with prospects, clearly define for them the problem you’re solving, your solution, and each of the buying stages, employing persuasion and trust to generate loyal, paying users.
When it comes to onboarding, the same concept applies. One thing you can do is send 1 email a day for X days or weeks that show them how to get started quickly.
By having a relationship and gaining trust with prospects, they will be much more likely to stick with you and become paid users.
A study even found that companies using drip marketing to nurture visitors saw on average a 451% increase in qualified leads. It says a lot.
Finally, just like you, I was looking for good drip marketing case studies not too long ago. Unable to find any, I wrote my own where I show how a SaaS company increased revenue by 30%, how a blogger made over $200,000 in two weeks, and how other companies are making millions in monthly revenue, automatically, with an efficient drip marketing system.
You can find them in my "Essential and Complete Guide to Drip Marketing": http://raphaelpaulindaigle.com/blog/drip-marketing-complete-guide/
Hope this was helpful, and don't hesitate to reach out if you have any questions :)