A bitten apple on a black and white background on a treeA bitten apple on a black and white background on a tree
An old brick wall illuminated by a flashlight beamAn old brick wall illuminated by a flashlight beam
Textured stone wall. an old stone. desktop backgroundTextured stone wall. An old stone. Desktop background
В математике: граница, отделяющая геометрическое тело от внешнего пространства. Наружная сторона чего-н..