The file transfer protocol, or FTP for short, is one of the oldest means of transferring data between systems. Although it's tried and true, it's also somewhat slow, but it's been around for so long that most institutions have the service in place so its ubiquity factor is high. SFTP or Secure FTP is a newer incarnation of the protocol which actually encrypts the data during transfer. SFTP is not only more secure, but also tends to be more reliable, so it is the recommended option when available.
The following link provides the details of using FTP, from both inside and outside the institution.