Third Person Camera in 2D Games
2D platformers are always in 3rd person - they wouldn't be 2D platformers if they had a different type of camera.
The camera used in 2D platformers are still 3rd person as the player sees the character they are controlling. However, the camera style in 2D platformers differ a lot from how third person cameras are used in 3D games.
In 3D games, the most common use of 3rd person cameras is over-the-shoulder shots or the camera following the character either from behind or behind and slightly above. In 2D platformers, the most common use of 3rd person cameras show you the character from the side.
The camera in 2D platformers is mostly static.
In a lot of 2D platformers, there is a middle space in the screen that is considered the area that the character should be in, and if the character moves out of this box, the camera is moved in that direction so that the character is in the middle of the box again. The focus in the box is usually more in the direction opposite to the way the character is facing - as it makes sense for the player to see more of what is ahead of the character than behind (so they can see what is coming immediately next).
Other 2D side scrolling games use a system where the character stays in place, with just movement/attack/jump animations and the