Handicap has two main meanings that are easy to confuse:

1. A condition that makes something harder to do. In golf, a handicap is a scoring system that lets players of different skill levels compete fairly. A beginner might get a 20-stroke handicap, meaning they can subtract 20 strokes from their final score. In horse racing, faster horses carry extra weight as a handicap to make races more competitive. The word can also describe any disadvantage: starting a project late might handicap your chances of winning, or not knowing the local language could handicap your ability to make friends in a new country.
2. An older term for a physical or mental disability. You might see this usage in older books or historical documents, but today most people prefer more specific and respectful terms like disability or particular descriptions like visual impairment or mobility limitation. Language changes as our understanding grows, and these newer terms focus on what people can do rather than what holds them back.

When you encounter handicap in modern writing, it usually refers to the first meaning: a disadvantage or a leveling system in sports.