It depends on some things that are situational, too. The type of offense run and the scheme, as well. Some OL's are small, athletic and able to slide around easily. Others are big, maulers that road grade.
The LT is a player that must have quick feet, long arms and able to hold off the LB who is almost always faster or the DE who is always almost as strong. Being that the LT sits back on his laurels to protect the pass he has to be big and able to absorb the hits and contact.
The LG is usually a fast on his feet and the most athletic of the crew. He's usually the one that will pull in many schemes. He has to slide side to side to assist in blocking regardless of the front.
the OC is some times the strongest and toughest. He takes on the bit NT's and DT's. He rarely pulls, he rarely does anything but give the ball to the QB.
RG and RT go hand in hand. The right side is where teams run the most. It's not exactly accurate, but IIRC stats show it was 51-54% at the very least that runs go to the right. That article was about 4 years ago.
RG is also able to pull, bigger then the LG and he also has the ability to take on LB's. Like the LG, they need good feet and balance to attack 2nd level defenders, and the wheels to get them to the defenders to lead block.
RT's are huge players. These are not usually big fatties. They are lions, they are D-5 bulldozers. The drive what is ahead of them but do not have the finesse of the LT. They're just big, dumb, and go forward.
If you'd like more specific info, I can go further. But, figure this might be good for ya.
Crap, I got a few more minutes.
Well, next time you watch football watch the OL. They'll point out assignments and they'll call out schemes. OL's have schemes just like in basketball. If the DT is playing between the LT and the LG and more closely toward the LG while the the DE is way outside of the LT, well, they may call a scheme which puts the OC covering the DT and the LT and LG covering the DE. Crap, any number of things could happen. A cross block, where the LT blocks the DT and the LG blocks the DE. The FB might go after the LB. Because, some times you get a LB coming forward to blitz - that's when the OL start pointing and calling out assignments. That's where Peyton Manning begins the whole "Omaha, Unicorns, Omaha, brunswick stew two dollars, I like turtles, Omaha."
Whats funny, you don't get it and most do not. Sure, he's yelling Omaha but it's not Omaha that matters, it's how many times he is yelling Omaha or if he says Unicorns he is calling off the Omaha. That may be telling his OL to block the LB because he is keeping the FB in the pocket to block and not come to the OL to assist, perhaps. Maybe it's saying the FB is going to block at the line where ever is needed, or maybe just go after a blitzing LB.
And, of course, if that blitzing LB is faking the blitz you have an exposed unoccupied LB and a mismatch - advantage defense because you just put a defender somewhere Manning did not anticipate - likely in coverage and perhaps on the route he just audibled to and that could be a problem.
Anything else ya wanna know with specifics, ask away.