Refers to the powdery residue left after something burns, such as from a fire, cigarette, or incense.
I dropped the cigarette ashes into the ashtray.
After the fire, the house was reduced to ashes.
Compound of 灰 (はい, 'ash') and 殻 (から, 'husk' or 'shell'), referring to the husk-like residue of ash.