A UserScript is a small program that modifies the way a web page behaves or looks. It is typically written in JavaScript and can be used to enhance user experience by adding features, changing styles, or automating tasks on websites. Users can install these scripts through browser extensions like Tampermonkey or Greasemonkey. UserScripts are often shared within communities, allowing users to benefit from each other's creations. They can be used for various purposes, such as blocking ads, improving navigation, or customizing the appearance of a site. This flexibility makes UserScripts a popular tool among web users.