Echelon form means that the matrix is in one of two states:
- Row echelon form.
- Reduced row echelon form
A matrix is in row echelon form if it meets the following requirements:
- The first non-zero number from the left (the “leading coefficient“) is always to the right of the first non-zero number in the row above.
- Rows consisting of all zeros are at the bottom of the matrix.
REF
https://www.statisticshowto.com/matrices-and-matrix-algebra/reduced-row-echelon-form-2/