Whatever you do, don't ask Denard Robinson
Passing Route names describe the pattern of the route the receiver runs. A receiver's route will usually have one or two cuts, which are a change in direction. Why should you listen to me? I have a 65 game winning streak in NCAA 2010 on All American mode including 5 straight wins against Michigan, and I just won my 5th straight NC.
These are some basic routes. Most routes are some sort of variation on these. Generally I find man coverage is harder to throw against than zone. With zone coverage you can usually rely on timing to find a guy with nobody around him when he hits a gap between defenders. It's a lot tougher to find open guys in man because it's not based on timing, so you have to watch about 3 or four of them at a time and being open doesn't mean nobody is around him, but that he has position between you and the defender and space where you can get the ball to him "where nobody else can catch it." I'm still trying to master the back shoulder fade that NFL QBs use so well.
Streak, Go or Fly
The Receiver runs in a straight line toward the end zone. The goal is to outrun the cornerback. If the defense doesn't use the safety over the top and your quarterback can step into his throw, you can usually lob a pass to him in stride and he can take it the distance. Takes time to develop though, so not effective against a blitz.
Michael Jenkins ran a Go route in 2002 against Purdue in the Holy Buckeye play.
Dig or In
A Dig route is where a receiver runs straight for a while and then makes a 90 degree cut to the middle of the field. The cut can be made at various intervals. These routes are good against man coverage if your receiver can fool the corner. If the corner's good though and has position ahead of the receiver, don't throw or it'll be picked.
An out route is the opposite of a dig route. The receiver makes a 90 degree cut to the sideline. Be careful with these. If you don't lead your receiver enough or have enough touch on the ball, you could be throwing a pick.
My absolute favorite route. If you're playing a team that runs a lot of zone, you'll want to use this route. A post route is where the receiver runs straight up the field and then makes about a 45 degree cut toward the middle of the field. Most zone coverages have huge open areas in the middle of the field and you should find your receiver with a 5 yard cushion around him. Rifle the ball at him as hard as you can and you've got 15+ yards. Mix it up to various receivers and DO NOT forget your tight ends - especially if they are blitzing you a lot.
Posts are good against man too if you receiver gets the inside position. Be careful of underneath zones though. Cover 1 can bight you here. If you see the middle linebacker drop straight back at the snap, keep half an eye on him.
Slant routes are helpful against man coverage. If you're receiver gets position, fire it to him. Should be good for 5+ yards. Watch out for outside linebackers dropping into zone though. Could be a recipe for a pick.
A flag route is kind of the opposite of a post. It's the same basic pattern: run forward and cut 45 degrees, but the direction is the opposite. This time the receiver cuts toward the sideline. Good against zone coverage.
A corner route is more complex. The receiver will start to run a slant route and will cut up the field toward the end zone and then will cut again to finish off like he's running a flag. The goal is to shake man coverage or find gaps in the zone. Practice these a lot because they take getting used to.
Drag routes are where a receiver will run across the field "east and west" very close to the line of scrimmage. These are good dump routes if everyone else is covered. Or if you wait long enough and they emerge out the other side after passing the linemen, they can get you some nice YAC (yards after catch). I find these are usually good for about 5-8 yards.
Curl, Hook or Comeback
A curl route is one where the receiver runs straight up the field and then stops and turns around to look at you. Against man coverage these depend heavily on timing. If you throw the ball at just the right moment, you'll get it there right as the corner is still back peddling and off balance so you're receiver has plenty of space to make the catch and possibly even a move for some YAC. If you're early it'll be incomplete, but if you're late, you're looking at a pick. Don't ever throws these late.
Against zone, though, they make for nice dump routes to a tight end or slot receiver as they can find a gap and just sit there. Then if none of your other routes pan out - or if you're under pressure - you can pop it to one of them.
Yardage depends on how deep the receiver runs before hooking and if they can get any YAC.
A flat route is where the receiver runs straight toward the sideline. If they're open and you get it to them in stride they can get some nice YAC.
A wheel route is the route that Anthony Gonzalez ran against Michigan in 2005 when he caught the ball inside the 5 to set up the game winning touchdown. The receiver runs laterally to the sideline and then streaks along the sideline toward the end zone. Hopefully his lateral movement will lull the defense to sleep and they'll forget about him while they worry about your flanker who's doing something more fancy over the middle. If you're lucky he'll be so wide open you'll piss yourself. These can be run form the slot, tight end, or even out of the backfield, like Maurice Clarett did against Michigan in 2002 on the game winning drive.
Option routes are much harder to master and rely on your understanding of what the defense does. In an option route, the receiver has the ability to decide what he's going to do and has about 3 different options. Usually it'll be something like Hook, Dig or Post or something like that. If you and the receiver make the same pre-snap and at-snap reads, then you have an advantage over the defense and he's usually open. Don't make the same read and it'll be incomplete to a spot where nobody is there at best, interception at worst.