There are three main protocols for file transfer between Internet-connected systems: SFTP, SCP and FTP. FTP is generally not recommended (except occasionally for anonymous transfers); the choice between the other two is partly a matter of personal preference, but SFTP is more widely used.
The main difference in practical operation between SCP and SFTP/FTP is that for SFTP or FTP you set up a connection and can then carry out a whole series of operations (including many which are not actually transfers, such as listing or even deleting files on the remote system). With many SCP clients, a single command normally transfers a single file or group of files, and to list files on the remote system, for instance, you have to login as a separate exercise. Some programs (for instance WinSCP) offer both SCP and SFTP options.
Servers and clients
To transfer files by any of these methods, you need to run a client program on the system which initiates the connection, and the system at the other end (the host) needs to be running a server program which can accept incoming connections and process requests from your client. Once connected, you can cause files to be transferred in either direction (host to client or client to host).
Generally, large multi-user systems can be expected to run an SSH server which accepts SCP or SFTP connections. Some will also run an FTP server, though for security reasons the access to these may be restricted (see FTP blocking for details for Cambridge systems). It may be possible to run the same servers on your own machine but this is not necessary for most users, who only need to run client programs. There are major security issues to be taken into account if you do want to run your own server.
Computing Service systems
None of the main Computing Service systems runs a plain FTP server. The Hermes filestore runs SSH servers for SFTP and SCP; DS-Filestore has an SFTP server but does not accept SCP. Note that the Hermes mailstore is not accessed by any of these methods; to transfer mail folders, use the facilities of Hermes Webmail.
Client programs are not provided on Hermes since Hermes does not allow users to run general programs. Client programs on the Managed Cluster Service include FileZilla, WinSCP and pscp on Windows, Fetch on Macintoshes; sftp, scp and ftp on MCS Linux and on Macintoshes.