When isSystemAccount is true for a user account?

Hi there

I got admin account details via velocity api($core_v2_user.Get("%{ Id = 2100 }")) and found out that it has "isSystemAccount" property with a "false" value.
What does "isSystemAccount" property with a "false" value and "isSystemAccount" property with a "true" value mean?
When the user account gets a "true" value for the "isSystemAccount" property?

[edited by: Ihor at 4:12 PM (GMT 0) on Tue, Jan 10 2023]