An individual would need an RPAL if they chose to acquire a restricted firearm. They fall, broadly speaking, into two categories. One is handguns and the other is restricted long guns—rifles and shotguns that happen to be restricted.
The individuals would generally acquire those for the purpose of target practice, but there are other reasons. For example, someone whose employment depends on a firearm will have to get the RPAL in order to use the firearm in the course of their employment.
There are a number of possibilities all laid out in the Firearms Act. Those are the two most common.