Music technology is part of my degree and I know all about click tracks! What it is, is basically a recording of a metronome tick that is used within recording software. That way, with each new part you record, the player can hear the same tick, and therefore play in time with all the other parts even though they were recorded at different times/locations. It’s better than just agreeing on the metronome speed, because after recording each part, you can export it out of the software with the tracks with your recordings. So if you use headphones, you can hear the previous parts with the click track as you are recording each new part. Just remember to delete the click track before exporting your final mix!
For click tracks I prefer using reaper. You’ll find a link for it here: http://www.reaper.fm/ You could also use pro tools, which is more popular among professionals, but I find it depends on how much CPU your computer has. It crashes on mine. http://www.avid.com/products