No free lunch in search and optimization

No Free Lunch is a phrase that means that if you want something, you need to work for it - nothing is free. In search and optimization, this phrase means that there is no single algorithm or method that works best for all problems. Every method or algorithm will work better in some situations, while not so well in others. So it's important to consider all the options and choose the best one based on the problem you're trying to solve.