difference between priority and non priority remarks?

like why should someone get a priority remark instead of waiting a little longer? is there some kind of deadline for something?

Some unis have a deadline on their offers

does it make a difference if i’m gonna take a gap year and reapply and not do clearing? or do i still need to get a priority remark so i can get the new grade (if it does change ) before i send in my next application? (i’d be early entry too)