At the end of regular play in a poker game the remaining players will be required to show their cards to determine who wins the pot. This is called the showdown.

Players expose their cards starting with the last aggressor, the player who made the last bet or raise. If the last betting round had no aggressor then the player immediately to the left of the dealer shows first. This means that no all players actually need to show their cards. Should a player already be beaten by one of the shown hands they may decide to simply muck muck their cards instead of showing.

It is also technically allowed that a winning player may muck their cards. In legitimate gameplay this is highly illogical and as such most online gambling does not allow it.

One player remains

Showdown only occurs when at least two players are left in the hand. Should enough players have folded leaving only a single player, that player is not required to show their hand.

Tournament all-in showdown

In tournament play a special rule is often adopted when all the remaining players are all-in. At the point when this happens all players current hole cards are exposed and the remaining cards dealt.

This rule exists to elevate tension, or intrigue, at the table. It is sometimes followed in ring games as well, though the poker rooms tend to vary in this regards. It is a divergence from traditional rules where a player need only show their hand if they have won.