Glossary
The Nuts
Definition
"The nuts" is the best possible hand available given the current board — the hand that cannot be beaten by any other combination of cards at that moment.
Why it matters
Knowing what the nuts is on a given board tells you the ceiling of hand strength in play. It helps you judge how strong your own hand really is, and how likely an opponent's aggressive betting is to represent something close to unbeatable.
Examples
If the board shows K♠ Q♠ J♠ 4♦ 2♥, the nuts is A♠10♠ — a royal flush, which is unbeatable on this particular board. On a different board, the nuts might just be top set or the top possible straight; it changes hand to hand.