A download accelerator is one which helps in increasing the download speed by establishing various links to the same download server. So virtually it is like splitting the file to be downloaded into various parts and downloading each part separately at the same time to increase the speed and reduce the time of download of the file from the internet.
In windows you can search for keyboard from start menu and open keyboard settings. Or you can go to Settings > Accessibility > Keyboard. In the keyboard settings window, toggle the switch that says "Use the Print screen button to open screen snipping". Hereafter whenever you press print screen button, you will be able to make a selection on the screen for a screenshot.