An elgato is basically a passthrough device for capturing the signal sent from a games console to a tv or monitor. This enables you to record your gameplay on a laptop or desktop computer so you can create videos with your gameplay.
If you're an avid streamer or content creator who wants one of the best consumer grade video capture cards on the market, then the Game capture HD60 Pro is certainly worthy of a purchase. If you don't want to tax your system, but want the best quality video and imagery, it would be hard to fault it.