Vogel's approximation method is an iterative method used to find an initial basic feasible solution for the transportation problem. It works by calculating penalties for each row and column based on the difference between lowest costs. It then selects the row or column with the highest penalty and allocates the minimum supply or demand to the cell in that row/column with the lowest cost. This process repeats, eliminating satisfied rows and columns, until all constraints are met. The document provides examples demonstrating how to apply Vogel's method step-by-step to solve transportation problems.