sir what is parallelopiped this is asked in the mathematics exercise of 8th grade but it is nowhere to be found in the book

In geometry, a parallelepiped is a three-dimensional figure formed by six parallelograms (the term rhomboidis also sometimes used with this meaning). By analogy, it relates to a parallelogram just as a cube relates to a square or as a cuboid to arectangle. In Euclidean geometry, its definition encompasses all four concepts (i.e.,parallelepiped, parallelogram, cube, and square). In this context of affine geometry, in which angles are not differentiated, its definition admits only parallelograms and parallelepipeds. Three equivalent definitions of parallelepiped are
 
a polyhedron with six faces (hexahedron), each of which is a parallelogram,
a hexahedron with three pairs of parallel faces, and
a prism of which the base is a parallelogram.
 
The rectangular cuboid (six rectangular faces), cube(six square faces), and therhombohedron(six rhombus faces) are all specific cases of parallelepiped.

a parallelepiped is a three-dimensional figure formed by six parallelograms.
The rectangular cuboid (six rectangular faces), cube (six square faces), and the rhombohedron (six rhombus faces) are all specific cases of parallelepiped.

See the image below. You will understand it better.