You may want to take a look at the:
As to key differences, I'm not too sure, not having really played pathfinder. The main ones I can think of are that classes can do a few more things (buffed from 3.5). 0 level spells are not expended when cast for cleric, druid, wizard etc, though they still need to be prepared. Point buy works slightly differently.
Favored Class: Each character begins play with a single favored class of his choosing—typically, this is the same class as the one he chooses at 1st level. Whenever a character gains a level in his favored class, he receives either + 1 hit point or + 1 skill rank. The choice of favored class cannot be changed once the character is created, and the choice of gaining a hit point or a skill rank each time a character gains a level (including his first level) cannot be changed once made for a particular level. Prestige classes (see Prestige Classes) can never be a favored class.
From what I've seen from game ads, two traits seems to be usual at character creation.
Bull rush, disarm, grapple, trip, sunder, overrun are Combat Maneuvers.
There is CMB Combat Maneuver Bonus for people using them, resisted by Combat Maneuver Defence.
CMB = BAB + str bonus + special size modifier.
CMD = 10 + Base attack bonus + Strength modifier + Dexterity modifier + special size modifier + miscellaneous modifiers.