BRP is so easy to learn I can tell you the core mechanic from memory:
Gameplay: Every skill is a percentile chance. Roll that number or under to get a success. If you succeed, put a little check mark by the skill.
Character Advancement: At the end of the session, find all checked skills. Roll d100 to "miss," rolling OVER your skill. If you roll over, roll a die (varies from BRP game to game, d4 - d10) and add that result to your skill for your new skill level.
End of BRP rules.
The result is that if you have a 5% skill, and you keep trying the skill, until one day you make it, you have a 95% chance to improve your skill.
When you have a 95% skill, you'll make it all the time, and have that check mark at the end of any game you use the skill, but you'll only have a 5% chance to improve the skill.
So no xp, and very little player control in how their character develops. Use a skill often enough, and it'll improve. Want to learn a new skill? Um, talk to your GM and maybe he'll come up with something, like move you from 0% to 5%.
And it's a long way from 5% to competent, which may be what Piratecat is referring to.