A "crush" is a strong feeling of attraction someone has for another person, often experienced during adolescence but can happen at any age. This feeling can make a person feel excited and nervous, as they may daydream about their crush and imagine what it would be like to be close to them. When someone has a crush, they might feel butterflies in their stomach or find it hard to concentrate when the person is around. It's a common experience that many people go through, and it can lead to feelings of joy or heartache, depending on how the situation unfolds.