Bandwidth is used as a synonym for data transfer rate, the amount of data that can be carried from one point to another in a given time period (usually a second). Different applications require different bandwidths. Standard definition video (480p) works at 1 megabit per second (Mbps), but HD video (720p) wants around 4 Mbps, and HDX (1080p), more than 7 Mbps.
So if you are in to streaming movies or online gaming you will want to have a higher bandwidth.
A good way to test your current bandwidth is to visit the SpeedTest website.