Man, why can't people let me take 10 minutes of their life to explain trivialities for me to grasp in 60 seconds, instead of me being the one to waste 10 minutes looking it up? Are you all really that lazy and self-centered?
Seriously, here's the first DESCRIPTION paragraph of man sftp:
sftp is an interactive file transfer program, similar to ftp(1), which performs all operations over an encrypted
ssh(1) transport. It may also use many features of ssh, such as public key authentication and compression.
sftp connects and logs into the specified host, then enters an interactive command mode.If this is not an ironic comment: RTFM is good for you and it's not a good habit to encourage people to ask for "pre-digested" knowledge just because "you" see no value in looking something up.