Passage Function: Door knob/lever on both sides of the door do not lock.

Entrance Function: Requires a key to lock/unlock the outside of the door knob/lever and a turn/push button to lock/unlock on the inside.

Now that you know the definition of the functions of passage and entrance, we can find out which one will work best for you.

Most of the time we suggest ordering the entrance if its for an exterior door along with a deadbolt, mainly because it's better security. You have 2 locking mechanisms on one door, which makes it twice as hard for an intruder. Some people think this is an absolute must. Others may not and just want the entrance function alone, which totally works too, but not as secure. The down side with wanting to order a keyed knob/lever is that you may not have as many options, as some of the styles don't offer a keyed entrance function. Like this very popular Sure Loc Juneau Lever...

 width=Don't worry, if you aren't too picky we can work around this issue. You can order a passage lever/knob (like the Juneau) along with a matching deadbolt to put above so you have at least some way to lock the door. It may not be quite as secure, but the deadbolts are really sturdy which can still give you plenty of security. If you want another good way to look at the passage function with deadbolt option... You can't lock yourself out! Unlike the entrance function where you can simply turn the lock from the inside, shut the door and forgot your keys... The passage has no lock and the deadbolts require a key to lock from the outside, so you can't lock yourself out even if you tried.

Whether you go with the entrance function or passage function you will have security and style. What you choose is up to you.

 
You can also find more options for an exterior door on this post.