How do Backlinks Tie in?

I know this is more than likely a dumb question. But I am tryin to learn about all of this stuff, so Imma ask questions.

How do backlinks help a website?
What are backlinks?
And how do you set keywords on your site?

Im sorry guys but I am trying to learn. I have used the search button but everything that comes up does not have the answer I need. I don't believe. Sorry guys, and thanks to anyone willing to help!

Basically a link to a site provides search engines the impression that your site is popular. The more links your site has equates to the more popular it is. That's just scratching the surface as there are many other variables such as relevancy, whether no follow is used in the link, what anchor text (link title) is used, etc. You may want to read more about backlinks at http://en.wikipedia.org/wiki/Backlinks

Best of success in your current and future ventures.

Thank you very much. That honestly cleared a lot up.