Someone please explain what the hell the difference is between the 2 and the 3. They both are not the point so what difference does it make? Side of the floor? Who cares. Marble is not a point guard and right now not really good at hitting the 3 but he can on occasion.
Not sure if this helps as it is very generic and does not always apply (especially with IA current roster) but here you go.
Offensively
The 1 generally would shoot from the top of the key, the 2 from either wing, and the 3 tends to run the baseline so 2 & 3 will get shots from either side of the floor depending on when they can work themselves open. Your 2 is often considered to be "the zone buster" or the guy who can keep a defense honest with his ability to drill the long-range jumper while a 3 is typically more of a slasher who prefers to put the ball on the floor and take it to the hoop.
Defensively
On the press, the 4 (sometimes the 5) is on the ball with the better shot-blocker of the two typically covering the back of the press while 1 & 2 pick up the opposing guards and either trap right away with the 4 or funnel the opponent toward the sideline so your 3 can jump over and attempt a 3/4 court trap. If the press is broken then everyone falls back into man and the 1 almost always goes head up with opposing point guard while the 3 is assigned to be the lock-down defender and takes either the opponents 2 or 3 depending on which is the better scorer as you don't want your shooter (2 man) to be too tired from chasing his man all over on defense that he no longer has the legs required to make his own jumper on offense. If you drop back into zone vs man, then the 1 & 2 are responsible for the top of a 2-3 zone while your 3 drops down alongside the 4 & 5 to help cover the opposing posts and/or baseline shooter on his side.