A web page keyword set is used by search engines to help them determine what a page is about and to help them know when to display certain results. The keywords are not readily visible to the page visitor because they are placed in what are called meta tags. A meta tag is html that is included in the header of a page and basically sits in the background when a page is viewed.
Here is a very simple html example. Note the "seo keywords, keyword optimization, keywords professional optimization, seo professional keywords". That text is in the meta tag named "keywords".
<META NAME="description" CONTENT="">
<META NAME="keywords" CONTENT="seo keywords, keyword optimization, keywords professional optimization, seo professional keywords">
<META name="classification" content="">
SEO for Keywords
Search engines relate keywords added in a web page to keywords people type when searching. They try to find the closest match for content, title, description, and keywords.
When writing your keywords be specific. If you don't have much chance in conquering the whole market for a keyword then try a keyword phase that narrows things down some. For example: instead of "mp3 player" use "ipod nano mp3 player"; instead of "nevada real estate" use "las vegas real estate" or more specifically "summerlin real estate". Use keyword phrases your clients will use to find you and stay specific to your page. Refrain from trying to capture the whole industry in one group of keywords on a page. Make the keywords relevant to that page.
Search engines don't give as much weight to keywords as they used to because people misused them and overused them. However, they still count so it is important to add them wisely.