What is a set of 3 in Phase 10 and how does it impact gameplay?

In Phase 10, a set of 3 refers to having three cards of the same number in your hand. This can impact gameplay by helping you complete certain phases, such as the "sets" phase, where you need to collect sets of cards with the same number. Having a set of 3 can also help you get rid of cards and move closer to completing the current phase.