Smell means: the object itself or the smell it emits

Gas is a gas, a volatile substance, a substance, usually a small molecule, so it is easy to become a gas. Taste is sensory perception, equivalent to a sensor. Refers to the change of physical quantity (physical quantity can be electricity, magnetism, light, length or volume, ion flow, molecular flow, etc. After the molecules act on the surface of the sensor, the generated signal is transmitted to the CPU (brain) through the nerve. So smell is not a substance, but a process of interaction between substances.

What kind of smell: generally describe this object (substance)/person; The unique smell emitted by itself.