The VGET service copies values from dialog variables in the shared pool or the application profile pool to the function pool variables with the same names.
The VPUT service copies values from dialog variables in the function pool to the shared or application profile pool.
Simply stated, you use the VGET service to retrieve a variable, or a list of variables, from either the shared variable pool or the profile variable pool. You use the VPUT service to update a variable, or a list of variables, into the same variable pools.
The shared pool contains the variables that are shared between ISPF applications. The profile pool contains variables that are saved to the user's profile dataset (ISPPROF) so that they can be retained between sessions.
In addition to VGET and VPUT, there are other services such as VDEFINE (which is needed whenever a CALL ISPLINK service is necessary, such as in COBOL or PL/I), VDELETE, VERASE, and VCOPY.