Some situations can give you advantage on checks, for example, if you want to pick the same lock again or if you have a suitable translation book when deciphering inscriptions.

If you have advantage, roll twice and take the higher result. The lower one is discarded.

Example: To jump over a chasm, you need to pass a Body STR - check of 14+. On the other side, your ally is ready to catch you and facilitate your jump. The GM decides that you gain advantage as a result. You now roll 2d20 = A 6 and a 15. Since 15 is the higher number, you take it and add your Body STR, which is 2. Your final result is 15 + 2 = 17. You pass the check.