The system process is responsible for the system memory and compressed memory in the NT kernel. This system process is a single thread running on each processor. It is the host of all kind of drivers (network, disk, USB).
The related file name is C:\Windows\System32\ntoskrnl.exe. The system process in Windows 10 has a additional task, it is compressing old pages of memory so that you have more free memory to use. That's why this process may use a lot of memory. If you see high cpu usage of the system process (more than 30%), than see this troubleshooting guide. The system process has always the PID 4 (Process Identification) in the Windows Task Manager, otherwise it is malware. 
