MSYS2 is a software development platform for Windows, providing an environment for building and running native software for Windows and other operating systems. It is based on Cygwin and provides an environment for building and running native Windows software including Windows applications, console programs, and libraries. It is based on a collection of Unix-like tools and libraries, including the MinGW-w64 toolchain for development and debugging of Windows applications, plus a collection of additional tools and libraries for development, compilation, and debugging of applications for Windows, Linux, and macOS. MSYS2 provides a complete environment for building, running, and debugging software for Windows, Linux, and macOS. It includes a rich set of libraries and tools, including compilers, linkers, debuggers, libraries, and an extensive package manager. It also provides a convenient way to install and manage third-party libraries, providing a comprehensive package manager for Windows and Linux. MSYS2 is designed to be an easy-to-use and comprehensive development environment for Windows, with its own package manager, an intuitive user interface, and a wide variety of packages to choose from. It is also designed to be lightweight and fast, making it an ideal choice for developers who don't want to be bogged down by a large, slow, and complicated development environment.
putty is ssh, while msys2 is a way to install a lot of posix related software on windows.