The real hook of "Brink," Splash Damage's multiplayer-centric shooter, is that any player can make a big difference to the rest of the team by completing secondary objectives, buffing squadmates or opening up shortcuts. And yes, shooting the other team helps too.
Because "Brink" is an action game, all of these varied objectives and status updates need to show up on the main screen without requiring the player to jump into several different menus. The end result is that the HUD can look a little overwhelming to a newcomer, which would explain why Bethesda released an entire video dedicated to understanding said HUD.
Rule number one: Watch those counters at the top right of your screen. The one at the top indicates how much time you have to complete the current primary objective. Let the timer go without completing that objective and it's Mission Failed. Other timers and meters will appear below that timer to indicate progress on the current objective (like how long until the planted C4 goes off), so it's a good idea to keep an eye in that general vicinity.
Rule number two: Watch your supply meter at the lower left of the screen. This is where the subtle HUD can easily feel overwhelming. Basically any powers that you have (such as healing friendlies or planting turrets) takes up part of your supply meter. If you have no supply meter, all you'll be able to do is fire your gun and run around...not very helpful to your teammates. The supply meter regenerates, so if you hang back a bit, you should have it filled in no time.
Rule number three: Watch the radar. As with games like "Call of Duty," enemies firing their unsilenced guns will show up on your radar, so keeping an eye on that for red dots is a good way to keep yourself alive. It's also great for checking the position of nearby friendlies, who may require a health or ammo boost.
The rest of the HUD is pretty intuitive. Most of the objectives guide you by the nose until you're staring at them, so you shouldn't worry too much about finding your way around. Just remember that SMART is your friend, allowing you to parkour your way up and over walls and other obstacles.