The Big M Method is a variant of the simplex method for solving linear programming problems. It introduces artificial variables and a large number M to convert inequalities into equalities. The transformed problem is then solved using the simplex method, eliminating artificial variables until an optimal solution is found. However, the method has drawbacks in determining a sufficiently large M value and not knowing feasibility until optimality is reached. It is inferior to the two-phase method and not used in commercial solvers.