Win32.CoinMiner is a mining client for windows that generate coins for the BitCoin decentralized economy by performing some highly complex computations. It may be dropped by Trojan:Win32.Comine.A and running without user knowledge. It uses system CPU intensively to generate coins.
Win32.CoinMiner itself isn’t a malware, but the fact that it works in background makes it popular among malware makers to install it to victims computers without their knowledge. Then it uses victims PC’s CPU and generates coins for cyber criminals. If your anti-malware program detected it on your PC and you haven't installed it – it might be a sign that your computer is infected by Trojans or malware. In that case you should do a full system scan. However, if you installed it to your PC, your anti-malware alert is fake-positive, so you can ignore it.
Win32.CoinMiner manual removal: