This is a demonstration of the Schlieren effect. This setup allows you to see changes in air density. The point light source is aimed at the concave mirror.
The concave mirror reflects to a focal point. There you use a sharp edged object to partially block the light which helps create a shadow effect that allows you to see air movement.
Schlieren flow visualization is based on the deflection of light by a refractive index gradient The index gradient is directly related to flow density gradient.
The deflected light is compared to undeflected light at a viewing screen. The undisturbed light is partially blocked by a knife edge.
When different objects — like a dry blower, an ice pop or a can of pressurized air — are held and used in front of the camera, it creates a beautiful effect.