FTP is the file transfer protocol. It can be seen that the FTP server is a server used to carry the FTP protocol. Find a high-end computer specifically as a container for accessing files, and other computers can access files on it through the network. This process is called building an FTP server.
You can use the ftp server that comes with Windows, which can be used with simple configuration, or you can download other software from the Internet to build such as serv-U, etc.