Hollow is most commonly used as an adjective.
Hollow means having a hole or empty space inside. Example: Each fiber has a hollow core.
Hollow can also mean having a depression in the surface of a thing; concave. Example: The old man had hollow cheeks.
Hollow is also a verb and a noun. Check your dictionary.
Empty means containing nothing; not filled or occupied. Example: He took his empty coffee cup back to the counter. The room was empty of furniture.