During job execution, you may want to use local variables. This way, you can have one job task store a value in a local variable that is picked up by a later job task.
These variables are 'local' in the sense that they cease to exist when job execution finishes.
To create local variables, add elements to the job's Input Parameter Set. Thus, Input Parameter Sets contain both values that are passed as an input parameter when the job is called, and local variables stored by the job itself during execution. Of course, it is also possible to have the caller pass an initial value as input parameter, and then have the job reset that value during job execution.
In complex jobs, it is good practice to add a comment in the External Set window that specifies which external set elements are immutable input parameters passed by the caller, which are local variables set by the job itself, and which are input parameters that may by modified by the job.