"Have to" is a phrase used to express necessity or obligation. It indicates that something is required or must be done. For example, if you say, "I have to finish my homework," it means completing the homework is essential. In everyday conversation, "have to" can refer to rules, responsibilities, or personal commitments. For instance, a student might say, "I have to attend school tomorrow," highlighting the obligation to be present. This phrase helps convey the importance of actions that cannot be avoided or ignored.