Backtracking is a technique for solving problems by incrementally building candidates to the solutions, and abandoning each partial candidate ("backtracking") as soon as it is determined that the candidate cannot possibly be completed to a valid solution. It is useful for problems with constraints or complex conditions that are difficult to test incrementally. The key steps are: 1) systematically generate potential solutions; 2) test if a solution is complete and satisfies all constraints; 3) if not, backtrack and vary the previous choice. Backtracking has been used to solve problems like the N-queens puzzle, maze generation, Sudoku puzzles, and finding Hamiltonian cycles in graphs.