what is the name of a 6 sided shape
A hexahedron! Seriously, latin it out. Hexahedron (6-sided shape) I think we normally call those cubes.
You can make many such shapes. One of them is the cube.
A 6 sided polygon is a hexagon
A 6-sided shape is called a hexagon.
An octagon is an 8 sided 2 dimensional shape. A cylinder with the base of a hexagon (6 sided shape) would be an 8 sided 3 dimensional shape.
A plane six sided shape is called a hexagon - whether you like it or not!