If you've ever watched professional gamers lock horns at big competitions then you'll know just how skilful they are.
Regardless of which game is being played the action is often fast and frantic.
What a shoutcaster does is make sure what's happening on screen is understandable to the fans watching at home or at an arena.
Chris Tunn is one of them and he tells us: "look at a football commentator, we do the same sort of thing but for eSports."
Chris told Newsbeat: "I used to play Call of Duty a lot when I was 16 and 17.
"I was at an event and one of the shoutcasters had to go home, and the owner of the event said 'does anyone want a shot at shoutcasting?'"
"I said 'I'll do it' and five years down the line I'm still being roped into doing it!"
In those five years eSports have grown massively with more professional players, more money, more exposure and more fans.
We've been behind the scenes with Chris at the Halo World Championships in London and seen just how slick his commentary set up is.
Already there are some fully professional shoutcasters but most, like Chris, fit events in around their 'normal' day jobs.
He tells us: "It is a viable career option, I would love to do full time.
"But it's one of those things that, if you are to get a full time job in shoutcasting, at the moment you are never doing it every single day.
"You have to do different things as well, for example my friend Richard has just got a job with a company where he is a community manager and shoutcasts at the same time."
With some professional gamers earning hundreds-of-thousands of pounds every year, shoutcasters are nowhere near that level.
So what makes a good shoutcaster?
Chris says: "You need to be able to speak well on camera for one and you need to have knowledge of the games.
"It's not necessarily just about commentating on what's in front of you but also you have to guess what's about to happen.
"You guess if players are going to move in a direction, and maybe meet up and have an important fight at a certain point of the map or a certain time in the game."
Shoutcasters normally work in teams of two and breakdown information coming at them from at least eight different screens.
Chris explains: "Primarily you have a play by play guy and a colour guy.
"The colour guy knows a lot about the game, a lot about the tactics and inside information, I then ask them why something was good or why it was bad."