Web forms are a web site tool that allows users to input information into the web site. Back-end programming often takes the user input, processes it, and returns some type of output. Take, for example, a site search. A text box allows the user to type in a search term. After clicking a button, the data is sent to a script which check with a database. Another script takes the resulting information from the database and presents it to the user in the form of a custom web page using HTML and CSS.