One of the more surprising rules of chess, when you see it for the first time, is "Pawn Promotion." This rule states that if you move one of your pawns all the way to the opposite end of the board, you can promote it to any piece you choose, except for a king.
How pawn promotion works
When a pawn reaches the opposite end of the board, the player gets the option to replace it with a new piece. Typically, players choose to promote their pawn to a queen, but they can also select a knight, rook, or bishop.
This option is available any number of times during a game, as long as you have pawns that can be promoted.
It's essential to keep your pawns safe and move them up strategically, aiming to reach the end of the board for promotion at the right time. Due to this rule, you can sometimes see two, or even more, queens of the same color on the board!
In almost all cases, promoting to a queen is the best choice. However, there are rare situations where promoting to a knight may be better, such as when you can deliver an immediate check to the opponent's king in a way that a queen could not.
Resources
Take a look at this game, where Chessbrah GM Aman Hambleton wins with six queens on the board!