A banker, Daily Mail* reader and immigrant worker are sat around a table looking at a large chocolate cake. The banker leans forward, takes a knife and makes two cuts that creates a 20% segment. He then takes the other 80% and puts it on his plate. After a while he turns to the Daily Mail reader and between mouthfulls says “I’d be careful if I were you. He’s after your piece.”
Competition for fixed or finite resources can lead to conflict. The simplest form of competition is a zero-sum-game in which me having more means you having less. I have +1 you have -1 so the sum of the competition is 0. Zero-sum, non-zero-sum and all other sorts of games have been studied extensively. Lots of clever people doing lots of clever maths. There are many applications in economics, politics, evolutionary biology amongst others. There’s even been a film made about one: the Nash Equilibria. OK, the film (A Beautiful Mind) was about John Nash, but Nash was awarded the Nobel Prize in Economics for his work on game theory.
The outcome of a game can depend on the rules, who is playing it (and how well) and luck. There are some games for which the only sane strategy is to simply not play