Backing Tracks for LIVE MUSICIANS!

Why I sometimes use backing tracks as a solo musician, where I get the tracks and how I modify them for live use! There is obviously a lot more that could be talked about on this subject (panning tracks for in ear monitors, adding click tracks etc) but this is a basic run down on why I use backing tracks, where I get them from and how I modify them to use in a live setting on an ipad.