Geth is the full node command line rpc client that runs underneth the Mist wallet. Geth won't use your CPU to mine unless you start it with the --mine command line parameter. Geth synchronizes with the ETH network and uses a lot of disk I/O, which can cause the client and system to become unresponsive. I prefer using the Parity wallet. It syncs MUCH faster than Geth and uses a lot less system resources. You can also use the Parity client with multiple chains like ETC and MUSIC.
www.parity.io