One pair, or shorter a “pair”, is a hand that includes two of the same ranked cards. One pair is the second-lowest ranked hand combination, right after just a high card. It’s followed by a two-pair hand.
Here’s an example to make it clearer. For instance, you’re playing a community poker game like Texas Hold’em in which the community board reads K, 10, 7, 4, 3.
You have a Q, 10 hand, while your opponent has Q, 7. While you both have one pair in this situation, you have a higher-valued pair and, therefore, win the pot.