A browser is the thing you're using to view this webpage right now...! But you probably already knew that. In short, a browser is a visual tool you use to interact with the internet. Most browsers are built on the open-source Chromium code base, which is maintained by Google, with notable exceptions being Apple's Safari and Mozilla Firefox. This just means that a lot of browsers will have the same features/functionality since they're running off a lot of the same code. In fact, Chromium itself is also a browser that you can use, if you want a lighter version of Google Chrome (however it will be missing a few minor features such as automatic updates).