Bottom line
The Force Readiness Assessment and Assistance Program (FRAAP) is a hands-on test of whether your SMCR unit can actually mobilize and deploy. It is run during a scheduled IDT period and looks at how well the unit handles the real mechanics of getting out the door: admin, logistics, supply, embarkation, transportation, and recall. If you are in an SMCR unit, expect this to happen during drill or right before AT.
What it means for you
This is a unit-readiness drill, not something you sign up for. The FRAAP checks the parts of mobilization that tend to go wrong when a unit actually gets the call: are records in order, can supply and embark move gear, does the recall roster work. You may be evaluated as an individual Marine and the unit is evaluated as a whole. It can run on a normal weekend IDT, or it can run right before annual training, and it may include moving the unit to a training site or a preselected location.