Rank of a matrix is a positive number that tells us how many rows are independent in that matrix, i.e., how many rows are not a linear combination of other rows or not a multiple of other rows.
It helps us to solve a system of linear equations and to determine whether the solution exists or not. If the solution exists, then it is unique or not can also be determined with the help of rank.
Rank should always be greater than or equal to 1 and less than or equal to the minimum of no. of rows and no. of columns of the matrix.