The apostles have come a long way since we last left them in Luke's gospel. Back then they spent most of their time staring blankly at Jesus as he enfolded the mysteries of Heaven and Earth. But now they're large and in charge
Now that Jesus has conquered death, the apostles are like, Oh, we get it. You were being literal about all that rising from the dead stuff. Who'd a thunk? Another forty days with the master himself leaves them prepared to lead his church on Earth. Fingers crossed, right?
No worries. For the most part, the apostles do a pretty decent job. They spread the good word about Jesus, heal sick people, lead the church, care for the poor, and are ready to lay their lives down for Christ at a moment's notice. Sniff. We're so proud.
But what's the only thing worse than being put to death? Bureaucracy. Yup. And it comes on the apostles pretty fast.
In the beginning, everyone is just hanging out with the apostles, sharing stuff, and singing kumbaya. But slowly, as the church grows, these guys are forced to start coming up with rules and assigning roles.
First up on the agenda: filling the vacancy left by one Judas Iscariot (see also: traitor, turncoat, and all-around horrible guy). See, Jesus specifically appointed twelve apostles. Eleven leaves you with an odd number, which just makes trying to seat people at dinner a pain. It also doesn't as neatly model the twelve tribes of Israel, so there's that too.
But what makes an apostle? Well, Jesus (the original apostle-namer) just booked, so you can't ask him. So Peter steps up and offers these guidelines. The new apostle can only be "one of the men who have accompanied us during all the time that the Lord Jesus went in and out among us, beginning from the baptism of John until the day when he was taken up from us" (1:21-22). Surprisingly, two names come up and the apostles pray and cast lots to pick the winner. Matthias, you are the twelfth apostle (1:26).
Does that mean that only men who fit that qualification can ever be called true apostles? That definitely leaves "The Apostle" Paul out. Shhh! We won't tell him if you won't.
The word "apostle" literally means "one who is sent," so that seems to include a lot of folks (including Paul, who was sent by Jesus himself). But in Acts it's usually the twelve who are referred to as apostles. Everyone else? Not as awesome.
While we're on the subject of ranks and rules, one of the other issues the apostles deal with is the growth of the church. As the church in Judea expands, some Christians start groaning that the food isn't being distributed properly to the poor. There's always a few complainers in every bunch.
The apostles don't have time to worry about stuff like this. After all, they're busy spreading the word of God. Seriously, people. So they appoint seven other men to be in charge of this (6:5-6). Next they've got to decide if Gentiles can join up (11:18). Then they have to sort out whether converts have to be circumcised (15:5). By the time Paul gets to Jerusalem (years later), he's speaking before "the apostles and the elders" (15:2). Bishops, deacons, and all kinds of fancy names aren't very far off.
The point of all this is that leadership is not easy. Twelve guys couldn't possibly spread the word of God all around the world. They're good, but not that good. They also couldn't make all Christians magically agree with each other. God himself still has trouble with that.