PuTTY is open source software that is available with source code and is developed and supported by a group of volunteers.
You can download PuTTY here.
You can login to any mikrotik device using your web browser as long as your of the IP address of the router. For instance the default IP for each mikrotik router is 192.168.88.1 this simply means that if you have a brand new router, and you connect to it either wirelessly or via ethernet port, once you type this address, a new page will open asking for authentication details the will enable you have access to the router configuration interface
The mikrotik Winbox is a downloadable application, and a small utility that allows administration of Mikrotik RouterOS using a fast and simple GUI. It is a native Win32 binary which has the ability to run on Linux and MacOS (OSX) using Wine.
What is Telnet?
Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else’s computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer.