Selenium will help you make the browser do what you do, on it's own. The simplest of examples, is you may want to make it such that you don't have to type in your name and password into a form anymore, therefore, you decide to "record" yourself doing it once and click replay every time you want to do it afterward.
Checkout this easy tutorial on using Selenium IDE. Learn my general strategy on creating, saving, and running tests. It also helps you decide what direction you want to go with a comprehensive list on the pros and cons of staying with Selenium IDE or moving on to more automated means.