What is it?
Local Security Authentication Server - lsass.exe
What does it do?
lsass.exe - It generates the process responsible for authenticating users for the Winlogon service. This process is performed by using authentication packages such as the default Msgina.dll. If authentication is successful, Lsass generates the user's access token, which is used to launch the initial shell. Other processes that the user initiates inherit this token.
You will not be able to end this through task manager!