Docking theory of olfaction
The docking theory of olfaction proposes that the smell of an odorant molecule is due to a range of weak non-covalent interactions between the odorant [a ligand] and one or more G protein-coupled odorant receptors (found in the nasal epithelium). These include intermolecular forces, such as dipole-dipole and Van der Waals interactions, as well as hydrogen bonding.
Source: Wikipedia — Docking theory of olfaction (CC BY-SA 4.0)