So, "guapo" is used for one handsome person, and "guapos" is used for multiple handsome people.
Here are some examples:
* "Los chicos son guapos." - The boys are handsome.
* "Ellos son muy guapos." - They are very handsome.
* "¡Qué guapo eres!" - You are handsome!
It's important to note that "guapos" can also be used to describe things that are aesthetically pleasing, like a beautiful landscape or a well-designed object. However, its most common meaning is related to physical attractiveness.