First, the more traditional "Tight End".
Tight End Physical Prototype: 6-5 245 4.7
The Tight End lines up just outside the Offensive Tackle usually and is often used more for blocking. Think of him as and undersized Offensive Lineman that can catch the ball but typically isn't required to stretch defenses with his athletic ability. Of course their have been and are exceptions, and the exceptional Tight End can do everything athletically that a receiver does, plus blocking. The University of Miami has a long tradition of turning out these kind of players - Bubba Franks, Kellen Winslow, Jr., and Jeremy Shockey to name a few. These guys aren't the norm though and teams that have guys like these don't often feel the need to incorporate an "H-Back" too.
Let's also define the H-Back so you can see why.
H-Back Prototype: 6-2 245 4.5
The H-Back is a across between a Fullback and a Tight End. You'll notice that the is prototypical H-Back is a little smaller and faster than the Tight End. He must still be able to block and catch, but is usually more of a running threat with the ball in his hands. He doesn't usually line up on the line of scrimmage. He will line up all over the back field: at Fullback, in the Slot, at the Wing. He's often used in motion. The H-Back can create confusion in a defense because he must always be accounted for, and because he lines up in different places and in motion, he can lull a defense into seeing him as a "blocker" then suddenly create a missed coverage assignment by sending him into a route.
The best H-Backs can do a little of everything. They aren't usually Tight Ends because of their size. They are decent lead blockers and pass protect blockers but aren't typically dominant "drive" run blockers.
Now, as mentioned above, teams with above average Tight Ends don't often use H-Backs. The simple reason is that they can be dangerous from the line of scrimmage. They can be dominating run blockers, get open, have good hands, and make yards after the catch. The thing you give up by using an H-Back is either lining up a smaller player on the line of scrimmage or taking a Running Back or Wide Receiver off the field.
You can use both effectively however.
One example is having your H-Back come in motion towards the Strong side alignment and block, overloading the defenses' numbers on a Sweep. Or bringing him towards the Weakside on a Counter, and having him release out into the flat for a bootlegging QB.
He can also line up as a Fullback in short yardage "Jumbo" sets.
Alignments and deviations are plenty when using the H-Back. They are popular in a Spread attack because they give the defense one more thing to have to account for - and because he lines up all over the backfield you have to be able to effectively communicate picking him up on each play. And if you're looking for a name to associate with the prototype H-Back, remember this one...Thor. He can do it all. The NFL has noticed too. The position is a perfect fit for him.
Anyway, hope this clears up the questions about the two positions. Come in to the Owl's Nest to discuss it further...