A pre-job is similar to a job but is used when you want to store elements that are used in more than one job.
Pre-jobs are useful in these ways:

We suggest that you create a pre-job on each of your job servers, so you can make use of the pre-job feature on each of your servers.

NOTE: RBA object/array defined for Jobs will appear as null for Pre-Jobs and as a result, either the Rule Set would crash or no report would be generated.