Hey Badrish, AutoIT is a third party tool to handle window based applications. It is a freeware written in VB-Script and designed for automating the Windows GUI and general scripting. It uses a combination of simulated keystrokes, mouse movement and window/control manipulation in order to automate tasks in a way not possible or reliable with other languages. AutoIt is also very small, self-contained and will run on all versions of Windows out-of-the-box with no annoying “runtimes” required!
Some times while doing testing with selenium, we get stuck by some interruptions like a window based pop up. But selenium fails to handle this as it has support for only web based application. To overcome this problem we need to use AutoIT along with selenium script.