Promotion

Promotion is where the pawn reaches its eighth rank and converted to a Queen, Rook, Knight, or Bishop of the same color. The pawn will be replaced with the new piece on the same spot. The choice of promotion is not limited to the opponent's captured piece, and the player is allowed to have more than a specific type of piece than the number of that piece from the startup. This means that a player is allowed to draw as many pieces as desired, but of course, there are limited number of promotion due to a maximum of 8 pawns. If a player has no more pawns, it's not possible for them to promote. A player is allowed to use an upside down rook (because it's already captured to symbolize the piece as a Queen.

Promotion to a piece
The Queen is the most common promoted piece, just because it is the most powerful piece in the game of chess. However, in a rare situations, where promoting to a Queen will result in an automatic stalemate, a player has can also promote a pawn to a Rook, Bishop, or Knight. Out of all of the games that are played worldwide, the chance of promoting a pawn to a various piece is shown below:

Only 3% are underpromotion. A player is allowed to promote a pawn to any piece they wish. A player could have a maximum of 9 Queens, 10 Pawns, 10 Bishops, and 10 Knights.

Underpromotion
Promoting to a Rook, Knight, or a Bishop is called underpromotion. Though these pieces are weaker than promoting a Queen, it still has an advantage under certain circumstances. Fork (for a Knight), preventing stalemate, slowing down checkmate are possible circumstances why promoting a Queen is not always a good idea.