You arrive at the airport, you're parked, you're ready to go, and ... you're waiting at the ticket counter. If it's within an hour or two of your flight, sorry, most airlines will make you check in at the ticket counter, which means waiting in those lines. But you can skip the whole thing if you check in online, which most major airlines will allow you to do within 24 hours of your flight's departure time.
When you check in online you can also -- and should -- print your boarding pass, or send a mobile boarding pass to your smartphone. That's another step done before you even set foot in the airport.