You gain XP from killing enemies, picking locks, finding Nirnroot, completing quests and so on.
Once you have enough XP, you level up and get some points to distribute.
nirnroots gain you anything other than quest progress?
i had no idea.
btw for oblivion XP isnt really a good term, cus its not really XP in that sense (in what i see as a fallout sense
)
killing enemies will gain you specific xp to the actual weapon you use. killing shitloads w your sword, makes you a sword-lord
while in a game like fallout, you just have to kill a lot in general, get xp, and use this xp to enhance any skill.
a thing i often do in oblinion, is to always eat any ingredient i find, toxic or not. it boosts my alchemy skill like hell.
jumping, sneaking and alchemy are skills that tend to shoot up without hardly any effort at all.