PuTTY is a free and open-source terminal emulator, serial console and network file transfer application. It supports several network protocols, including SSH, Telnet, rlogin, SCP, and SFTP. PuTTY allows users to securely connect to a remote computer or server and perform various tasks such as running commands, transferring files, and managing network configurations. The software has a simple user interface and can be customized with different fonts, colors, and key mappings.