This app is really easy to use, you just have to look for any video in the search bar of the app and press the green arrow located on the bottom part of the screen. At that moment you can select the video quality you want to download. It normally has many different resolution options adapted to the different Android devices compatible with the application.
The downloaded videos will be stored on your SD card by default, but you can move them around from one location to another, however suits you best. TubeMate YouTube Downloader is a very easy-to-use video downloader whose main strong point is exactly that--you can have get your hands on any video in seconds.