How can I find out about Competition?

[Korte]

Firstly we must state what is your competition:
Your competition is the site that want to rank good for your keywords. You should optimize your website better than they else you are going to lank lower than they and they receive more traffic. (this traffic could be yours if you would optimize your website).

How to find your competition?
Just do a Google, Yahoo and Bing search for your main keywords and you will find your competition. Every single website above you and the next 3 websites under you are your big competition, the rest of the websites ranking lower than you are small competitiors because your website already works better and you don't need to "beat them" but they can still improve so watch out for them.

How to find out more about them?
Check their Alexa ranking, Pagerank, check every single ranking factor and find out why they rank better and improve your website.