A **homophone** is a word that **sounds the same as another word** but has a **different meaning** (and often a different spelling).
For example:
* **to**, **two**, **too**
* **their**, **there**, **they’re**
* **flower**, **flour**
* **see**, **sea**
So when you *hear* them, they sound identical — but when you *read* or *use* them, the meaning changes.