Trials of Osiris are the pinnacle of Player Versus Player.

For the uninitiated, Trials of Osiris is a competitive mode two teams, formed of three players, fight with a limited number of lives in the Elimination format. The event starts every Friday after reset and continues through the weekend until reset on Monday.
At the start of every run, players are provided with a card. Three losses on this card means that your run will come to an end.
Luckily, you can always get in-game support from the Destiny 2 carry. The pros will help you get the weapon need and handle the routine of the game.