Long-tail keywords are search phrases, rather than one or two words. If you are planning to promote an online poker course for example, you might do some keyword research and decide that the term "online poker course" has too much competition from existing websites, but articles based on things like "When to push during a sit-n-go" don't have as much competition and may yield more traffic.
There are many ways to be successful as an affiliate, but this article lays out the process that we have found to be the most reliable and sustainable while still being very inexpensive. Many affiliates try to skip steps 2 & 3 and go straight from picking a product to immediately promoting it. This makes it really difficult to succeed, and doesn't set up your business for success, so make sure to implement the steps in the order they're listed here.
This is a way to help you create a website for your own product that essentially integrates with Clickbank to make selling this product easier. I think this is a cool idea, and for folks looking to create their own digital product, this would be a worthwhile investment. But remember, you're now paying $47/month for CBU members area ($564 per year), PLUS $594 for the builder. Your yearly cost of business operation just jumped to over $1,000. Also, remember that this might lock your site into their builder, so if you decide to change to outside hosting at some point, I'm not sure how that process goes.