What do you mean by feasible solution and optimal solution

Feasible solution: Any subset that satisfies some constrains is called feasible solution. All feasible solution is not optimal. It considers one input at a time. Finding a feasible solution may be the hardest part of the problem.

Optimal solution: A feasible solution that either maximizes or minimizes a given objective function is called an optimal solution. All optimal solution is feasible. It considers the input in an order, determine by some selection procedure. Finding an optimal solution may be the simplest part of the problem.