I am not sure but those guys may be expecting an answer like 3 system
viz. standard JCL, JES2, JES3. Though many of their commands are identical they differ in few ways.
We need to go back to MVS history.This was long back when MVS didnt have effective schedular, So people were using JES2 also known as HASP and JES3 also know as ASP (I forgot the correct full forms). They are mutually exclusive. When u have a single processor u use JES2 subsystem whereas if u have multiple processor u need to use JES3. All commands specific to JES2 begin with a /* where as command specific to JES3 begins with //* followed by no space. Todays MVS has integrated both these sub system and so within a single JCL u can use our standard JCL as well statements from any of these systems. One thing why even today we use some of the statements from these subsystem because they give us more control on environment.
This is from my memory. If u refer to the JCL reference manuals u will find more stuff about them. Expert plz. add.....
You should have asked the interviewer this question. Don't be afraid to ask them to clarify. You could have something like: "Do you mean the kinds of statements in JCL, JOB, EXEC, DD? Or JES2/3 control statements?". Who knows what he meant, except him.