What do poison counters do in Magic: The Gathering and how do they affect gameplay?

Poison counters in Magic: The Gathering represent a different way to win the game. When a player accumulates 10 or more poison counters, they lose the game. Poison counters can be given to players through certain cards and abilities. This mechanic adds a strategic element to gameplay as players must consider both traditional life points and poison counters when planning their moves.