Each player gets two Rooks, which start on a1, h1, a8, and h8. They move in straight lines on ranks and files only. The diagram on the left shows the movement options available to the Rooks. They can capture any opposing enemy piece that stands in their line of fire, but cannot jump other pieces.
To capture an enemy piece, remove it from the board, then move your capturing piece to the square where it stood. (Of course, you can't capture your own pieces.)
Here, White's Rook has moved from e5 to a5, and Black has captured White's Rook on b3. In chess notation, Rooks are referred to as 'R', and captures include the letter x. These moves would be written as Ra5 and Rxb3.