What dose it mean when someone says you rock?

When someone says "you rock", they mean that you are awesome, cool, or great. It is a positive expression that is used to compliment someone. It is often used to express admiration or appreciation for someone's actions, achievements, or personality. It can also be used to express support or encouragement. For example, if someone says "you rock" after you give a presentation, it means they think you did a great job.