Cricket is the game of enthusiasm and in India people are just crazy for the same. The game has set format and it must be followed from ground zero. Umpires are the backbone of the game because they are the decision makers. Lots of time we have seen the examples of amazing decisions. They work under huge pressure and obeying their orders is the primary job of all cricket players.
If we discuss by keeping the ground condition then there will be 2 umpires who take care of most of the decisions but in nearby years it has been seen that sometimes daisy conditions come and umpire takes wrong call. To make it more convenient, the provision of third umpire is added.
Hence whenever the captains do not get satisfied with the decision of umpire then they may take a review and third umpire will take a final call.
Apart from that, sometimes the run out visibility does not clear and to avoid the discrepancies, the filed umpires pass it to the third umpire. Third umpire judges the ball from all dimensional view and then a final call is made. Umpires are the one who controls the whole game.