The quote addresses the misconceptions others may have about your abilities. "They laugh at you because they have no idea what you're capable of" suggests that people may underestimate your potential and mock you due to their lack of understanding.
The quote speaks to the importance of self-belief. It implies that while others may doubt you, you know your true capabilities.
In essence, the quote celebrates the power of self-confidence. It underscores the idea that others' opinions should not define your worth, and that proving them wrong through your actions can be a rewarding experience. This sentiment reflects the notion that resilience and determination can lead to surprising achievements that may change others' perceptions of you.