For those who are familiar with basketball, the three positions in a game of basketball are guard, forward and center. The guard and forward positions had sub positions (point guard, shooting guard, small forward and power forward). If you're playing high level basketball (NBA, college, top high school teams) your position generally reflects the skill set you bring to the game of basketball.
However, in most adult basketball leagues, your position if sometimes determined by height / weight as much as skill. If you're a big and tall guy, you're usually going to be a center or power forward. If you're a decent shooter / ball handler / reasonably tall, you'll probably be a shooting guard / small forward. If you're a guy who can dribble and pretty short, you'll be the point guard.
Drilling down even further, Asian adult basketball leagues are a little more different. There aren't any Yao Ming's running around though you'll get a few 6'3" or taller guys ever now and then. But the reality is that most player fall between 5'6" and 6'1".
For me, I happen to stand around 5'10" and generally an shooting guard / small forward on offense. I usually defend point guards, shooting guards and small forwards on defense. For our Thursday night basketball league this sping, I am probably the tallest guy on my team. With the other teams having tough post players, I end up guarding the perimeter AND the post players.
Last night, my team played my friend's team in our league. My friend is 6'1" 180 pounds. He can post and has some guard skills. Seeing I was guarding him, my friend tried to post me and I had to battle just to keep him away from the basket. Alas, I got into foul trouble and later switched to guarding the point guard.
It was definitely a rough night on the court as my team lost 78-72. I scored 14 points but was somewhat beat up banging with the big boys inside and chasing the guards outside. I don't mind the challenge but being an older guy, I can't bang like I used to.