What are the rules for MTG counters and how do they affect gameplay?

In Magic: The Gathering, counters are used to track various effects on cards or players. They can represent things like 1/1 boosts, damage, or other abilities. Counters can have a big impact on gameplay by changing the power and toughness of creatures, keeping track of damage, or adding special abilities. Players must pay attention to counters to make strategic decisions during the game.