Chapter 1 - Systems of Linear Equations - 1.2 Gaussian Elimination and Gauss-Jordan Elimination - 1.2 Exercises - Page 22: 24

This matrix is in a Reduced Row-Echelon form.

This matrix is in a reduced Row-Echelon form because 1) In the bottom part of the matrix there are only zeros. 2) Each 1st nonzero element in each row is $1$. 3) In the column of those leading $1$-es the rest of entries are zero.