Keywords are the words which people use when they search for something on the Web. For example, when they search for 'shoes', the word 'shoes' becomes a keyword. Now, if you have a site about 'shoes', that's a keyword for you, too. What you need to do is to make sure that this keyword is used often in your site. When a person searches for 'shoes', the search bots will look up all the sites with the word 'shoes' in the content. How your site will rank in the search results is another story.