Pull-ups and chin-ups are both great strength-building bodyweight exercises, but they're not the same exercise. People tend to use them interchangeably, but the differences are distinct enough that you should avoid lumping them together.
Image by 316th ESC.
Both exercises look similar and target your upper back and biceps, but they differ in how those primary muscles are worked and the grip you use.
- Pull-up: In a pull-up, you use an overhand grip (basically, your palms face forward). There's greater emphasis on using your lats to get up, which tends to be more difficult for people.
- Chin-up: Chin-ups use an underhand grip (both palms are face you) and emphasise the biceps more. Most people will find chin-ups to be easier.
These differences don't necessarily make one better than the other -- you just end up training your upper back (lats) in a different way, and if you alternate between them, also lets you evenly work out different parts of those same muscles. If you get elbow pain, you might experience less pain by switching to a neutral grip (palms facing each other).
Pulls Ups vs Chin Ups -- What's the Difference & Which One Is Better? [A Workout Routine]