The secure copy command (run using scp) is a Linux command that allows the transfer of files between two computers. This can be locally to a remote server, from a remote server to a local location, or even between two remote servers.
When copying to or from a remote host scp uses ssh for the data transfer. This means that authentication is required, but the files are copied in a secure fashion. When starting a scp request the command first sets up an ssh connection to the remote location, which is then used for the rest of the transfer.