The outward or external appearance or surface of something.
Superficies is about how something looks on the outside.
Examples:
The superficies of the water was smooth.
The superficies of the table was shiny.
The superficies of the rock was rough.
The superficies of the cake was bumpy.
The superficies of the moon looks bumpy, but it's actually very smooth.
The superficies of the leaf was green and shiny.