In the online world, keywords function as a summary of what your entire web page is about. They are just one way search engines know what the rest of your site should be about. If you have a website that utilizes a variety of related keywords, the Google gods are believed to show favor upon you and rank you higher on the search results pages.
The search engine algorithms have become pretty sophisticated. They expect your keywords to be relevant throughout your website. If your online store sells shoes, you know that’s a pretty broad word for an accessory that has a lot of different variations. So you use “women’s winter boots” as a keyword on one page, and “summer wedge sandals” on another, and the search engines will appreciate that you didn’t use just the word shoe over and over again. Plus you’ll have a better shot at being seen by people searching for the perfect pair of summer wedge sandals.