ECO 550 Strayer University Game Theory and its Application Discussion

I’m stuck on a Economics question and need an explanation. So what is GAME THEORY and how do businesses uses games?  In the text, we consider a sequential-movie game in which an entrant was considering entering an industry in competition with an incumbent firm. Consider now that the entrant, if fought, has the possibility of withdrawing from the industry ( at a loss of 1 for the entrant and a gain of 8 for the incumbent), or staying at a loss of 5 for each player). What is the equilibrium of this game? Discuss if the entrant is better with or without the ability to withdraw.