Use cases can be divided into two types. It is not necessary, but if someone ask you to do that, it is possible.
System use case represents the use cases which are done by the system(not manually).
For example: In a online hotel reservation system a user books a room. So the booking is a system use case and the user is a system user.
Business use case represents the use cases which are done manually. It is not necessarily done by the system.
For Example: Manual hotel reservation via telephone call. A user calls the hotel and books a room. Here telephoning is not a system use case, because it is not done by the system. The user is also not a system user, because they do not interact with the system.