An ally is someone you team up with. ln the case of the Hunger Games you can team up with other tributes (players, contenders) and you became an ally to each other.
Alliances are sometimes formed in the Games.
Sometimes, the strong ones form an alliance to hurt another tribute. Then, once the weak has been taken out, the alliance is broken and it is easier for them to take on one another. It is a common strategy for Careers (tributes who planned on the Games their whole lives in order for them to surely win). And that is not always the best strategy.
but i say to at lase trust them if you want a ally
