It seems like you're referring to the game "Tic-Tac-Toe," which is often abbreviated as "XO." Here's a description:

**Tic-Tac-Toe (XO):**

*Tic-Tac-Toe,* also known as *Noughts and Crosses* or simply *XO,* is a classic two-player game played on a 3x3 grid. The players take turns marking a cell with their respective symbols, usually "X" for one player and "O" for the other. The objective is to get three of their symbols in a row, either horizontally, vertically, or diagonally.

**Rules:**

1. The game is played on a 3x3 grid.
2. Players take turns placing their symbol ("X" or "O") in an empty cell.
3. The first player to get three of their symbols in a row wins.
4. If the grid is filled without either player achieving three in a row, the game is a draw.
5. Players cannot overwrite their opponent's symbol once placed.

**Objective:**

The main goal is to strategically place your symbols to create a line of three, blocking your opponent from achieving the same. The game requires critical thinking and is often used as a simple yet engaging activity.

**Variations:**

Tic-Tac-Toe has various size adaptations, like 4x4 or 5x5 grids, which increase complexity. Additionally, there are more advanced versions of the game, such as "Ultimate Tic-Tac-Toe," adding layers of strategy.

It's a popular and timeless game due to its simplicity and quick play, making it a common choice for educational purposes, as well as a casual game enjoyed by people of all ages.