There are two ways a coronavirus can be transmitted via air i.e in droplet and in aerosol form.
The coronavirus is airborne for a few seconds after someone sneezes and it travels for some time before gravitational forces pull it down.
Someone close enough for the virus particles to reach in that brief period can, therefore, be infected.
Particles can live on surfaces for several hours whereas an aerosol is present in a different physical state, in this, the particles are held in the air. Fog is an aerosol and the water droplets are suspended in the air.
The suspended particles stay for hours on the surface and anyone who comes in contact with the particles gets infected.