PuTTY is an SSH and telnet client, developed originally by Simon Tatham for the Windows platform. PuTTY is open source software that is available with source code and is developed and supported by a group of volunteers.
Here are the PuTTY files themselves:
PuTTY (the Telnet and SSH client itself)
PSCP (an SCP client, i.e. command-line secure file copy)
PSFTP (an SFTP client, i.e. general file transfer sessions much like FTP)
PuTTYtel (a Telnet-only client)
Plink (a command-line interface to the PuTTY back ends)
Pageant (an SSH authentication agent for PuTTY, PSCP, PSFTP, and Plink)