Haven't flown since I was eight, what's the airport process?

First of all, what the hell is a "check in"?
Alright, basically I don't remember the airport process.
I bought the tickets from Travelocity, not the actual airline. Plus, I'm traveling United Airlines (domestically, obviously) from Orlando(MCO) to Newark(EWR). I want to know if this changes the process any differently? How do I get my boarding pass?
Since Travelocity and United Airlines both allow Passbook on iPhone, can I use that as my boarding pass? SOMEONE EXPLAIN THIS TO ME OMG I don't know WHAT TO DO

How old are you now lol? But all you do is get in the airport go into the right terminal i.e United terminal, AA terminals, etc. And there should be buses and taxis that can help direct you. There are loads of people to help you out too. Like the Police the people AT the airport (or inside) and a lot others. But all you really do is get into your correct line and wait for about 10 minutes (varies on what time you get to the airport.) And be sure to get to the airport 2 HOURS early it helps trust me. Or you can go to the booking counters and get your ticket manually from there nothing changes really its a lot quicker too…

When you bought the tickets on line, they sent you an email with your confirmation umber on it. Print that email and take it with you. Enter the airport and go straight to your airline's desk… There are huge signs hanging from the ceiling. Give them the email with your confirmation number. Give them the bag you want to check… This process is called "checking in." They will give you a boarding pass. Follow the signs to security, get in line and go through security. When you have finished in security look up… Look at the signs to find the way to the gate listed on your boarding pass. Walk to the proper gate and wait. Shortly before time to board an airline employee will come to the small desk in the waiting area… You can go to that person and show your boarding pass to be sure you are in the right spot. Then wait a few minutes til they call time to get in line to board. There are 3 steps in the airport… The airline check-in desk, security, and the waiting room at your gate. See below for the liquid rules.

Entry and passport ticket check>Check in and boarding pass issued> security pass> shops > boarding gate> board plane> fly.

Charlie's description was perfect.