What does FTP mean and how do I use it?

I've heard a lot about FTP lately. I plan to host a Minecraft server and asked the support if I can use my own plugins. I was told that I can use my own plugins using FTP. What does that mean? And how do I use it?

I'm a bit later, though, ftp is a method for the pc that you can use to connect to a Minecraft server, for example, and then upload files to the server.