Cryptomining is a type of hacking, where, the hacker instead hacks into the user's computer to mine crypto-currency, such as bitcoin, rather than to steal the user's personal information. Cryptomining can cause the user's computer to run slower, as it takes up CPU memory.
Most of the time, the user is unaware of cryptomining when it is happening, it is considered to be a theft of resources, as the hacker is using the user's resources for his/her own good. Cryptomining involves running the user's CPU and GPU at a higher capacity, which allows for more crypto-currency to be mined. If Cryptomining is prolonged enough, the capacity of what the computer can handle will decrease, and the user's computer will run slower. This can shorten the lifespan of the computer, or in extreme cases, even brick or severely damage the computer.
Removal of cryptomining is difficult. The user can only slowly troubleshoot it. The cryptomining program disguises itself as a legitimate process/injects into a legitimate process in Task Manager, making it much harder for the user to find the process of the cryptomining program. It is easier to use Process Explorer to find the parent process and the file location. Antiviruses can also remove the cryptomining program.