Ssh

SSH, which under FreeBSD is generally the version found under the openssh-portable port, is the command-line tool used to access a shell prompt on a remote network computer. Doing this is commonly referred to as "shelling in" to the remote server and can be done from a computer that is not unix-based (such as Microsoft's Windows OS or Apple's [OS X].

SSH distributions also typically include such as the command scp for copying files from remote computers, and/or piping arbitrary data streams through SSH tunnels.

There are many ssh programs such as TeraTerm SSH (which doesn't support the cryptographically stronger SSH2 protocol but will also allow you to connect via a serial port), MSSH, secure iXplorer, FileZilla (an SFTP GUI), WinSCP (which does SCP via a GUI), and the commercial (but free for non-commercial use) client from SSH Communications.

By far the most common non-Cygwin Windows equivalent to OpenSSH is the freeware (open source?) application PuTTY, although many commercial equivalents are also available.