Vim is a text editor that has been in use for a very long time. It remains popular among developers because of it's speed in making changes, once you know the keystrokes and commands to get things done. A main aspect of this is that you can keep your hands on the keyboard at all times, which makes for faster input than switching to a mouse and clicking through an interface. For example, you can quickly open a file by typing part of it's name and autocompleting with tab, instead of navigating through a file tree to find the file. There are other shortcuts too, like autocompleting brackets, or showing you available functions.