Screen Shot Tool PRO is described as 'This is the handiest way to screen capture, edit selected areas on the screenshots, and sharing with others' and is an app in the Photos & Graphics category. There are more than 50 alternatives to Screen Shot Tool PRO for a variety of platforms, including Windows, Mac, Linux, Google Chrome and Firefox. The best alternative is ShareX, which is both free and Open Source. Other great apps like Screen Shot Tool PRO are Greenshot (Freemium, Open Source), LightShot (Free), FastStone Capture (Paid) and Snipping Tool (Free).
You grab Screens or Windows using the standard PrtScn and Alt-PrntScn keys and MGrab will intercept the saved data as it is sent to the clipboard and put it into your chosen folder as a BMP or JPG file leaving the clipboard free for you to take another screenshot.