Putty is one of the Best Terminal Emulators available today. It Supports different types of Network Protocols such as SSH, FTP, SCP, Telnet. It is used as SSH Client to connect to Your Linux server or for some other purpose.
SSH is available by default in Mac and Linux or Unix. Although you can use terminal for SSH connections still there are some benefits using putty such as other clients don't keep connections alive whereas Putty does. Also it is cool to use Putty as your SSH client if you are doing some Amazon AWS, VMware ESXi or CISCO Stuffs, transferring files, managing files on a server or whatever.