What does a mask mean?

Mask, mask, camouflage; Wear a gas [fire] mask. Masked people pretend to be spherical face models or incarnations (usually grotesque) heads or black parts around the mouths of dogs, foxes, etc. Bunker brush mask; Shading frame; Screen frame time scale (in front of TV picture tube), time scale self-mask, separation word psychological personality mask (cosmetics) electronic (integrated circuit layout) template ship stern protection wood

A layer of snow on the ground.

A layer of snow covering the ground.

The robbers wore masks.

The robber wore a mask.

Nurses wear masks and tight white hats.

Nurses wear masks and white hats that tightly buckle their hair.

These jokes are masks to hide his sadness.

Jokes are a way to cover up his inner sadness.