The Mail Online have decided to ridicule the 5th official with an article that shows a video of a 5th official warming up and making a bit of a joke out of it whilst using the title “Really, what do they do?” which is never answered in the article.
The main objective of the 5th official is to be in a position where they can see things such as “Ghost goals” and to help referees make key decisions in the penalty area such as a handball incident whilst a player has his back to the referee. This then aids match control as a referee has extra help and can make correct decisions.
They also must be available to replace an assistant referee if needed, a duty which was previously held by the 4th official. This changed as the 4th officials role has become more and more important. A 4th official has now taken on new duties such as been the person between the referee and each clubs’ bench.
I believe the only reason these types of officials where brought in was to fill the void left by the lack of goal line technology so until this is brought in the 5th and 6th official will cover this. Once goal line technology is brought in their use will change and their purpose will be to solely aid the referees decision making by offering a different angle.