Originally posted by Dub J
Basically hitting certain caps is important so you can maximize auto level gains.
http://wiki.goallineblitz.com/index.php/Leveling
This and, more simply put, it is the point at which the cost in SP's to raise a skill increases by 1.
All skills start at costing 1 SP to raise any particular skill by 1 point. Once you hit the 1st cap (skill at 48), then it now costs 2 SP to raise that skill by the same 1 point... and so on and so on. Hope that helps.