1. Row Echelon Form: There can be more than two <em>row echelon forms</em> of a single matrix, so different sequences of row operations can lead to different <em>row echelon forms</em> of a single matrix.
2. Reduced Row Echelon Form: It's unique for each matrix, so different sequences of row operations always lead to the same <em>reduced row echelon form</em> for the same matrix.