When something disappears, it goes away and you can't see it anymore.
Disappearing can make people feel surprised or worried. It can also be like a magic trick.
Examples:
The magician is disappearing!
The sun is disappearing behind the clouds.
The cat is disappearing under the bed.
The cookies are disappearing from the jar.
The whole city is disappearing into the fog.
My toys are disappearing into the closet!