"Won't" is a contraction of the words "will" and "not." It is commonly used in English to express a refusal or a decision not to do something in the future. For example, if someone says, "I won't go to the party," it means they have decided not to attend the event. In addition to expressing refusal, "won't" can also indicate a lack of willingness or ability. For instance, if a child says, "I won't eat my vegetables," it shows their unwillingness to eat them. This contraction is widely used in both spoken and written English, making it an essential part of everyday communication.