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.
If you have an e-book or online course that you'd like to promote, ClickBank makes that easy. Once you sign up as a vendor you can list your product with them and set the commission percentage you are willing to pay to anyone who chooses to market and promote your product for you. Once your product is listed, other ClickBank users will start promoting it on their own websites. This will drive traffic to the sales page on your website and hopefully result in sales.
ClickBank is one of the most unique and diverse affiliate programs on the planet. Since they only deal with digital products, you get all sorts of vendors from all walks of life, with products that can fit almost any niche, or even create new niches. This means that no matter what type of blog or website you have, chances are you’ll be able to find a product that lines up with your audience.
If you're ready to enter the ecommerce fray, you could sell your own stuff. Of course, along with selling your own stuff on your own website comes a whole slew of both responsibilities and technical configuration and requirements. For starters, you'll need a website and a hosting account. You'll also need a merchant account like ones offered by Stripe or PayPal. Then you'll need to design that site, build a sales funnel, create a lead magnet and do some email marketing.