This is a line. It has one dimension. All one dimensional shapes only have length. The only 1D shape is a line, whether straight or wavy.
This is a rectangle. It has two dimensions: length and width. All 2D shapes have an area but no depth. Some 2D shapes are triangles, rectangles, pentagons, etc.
This is a cube. It has three dimensions: length, width, and depth. All 3D shapes are solids.
Each half is a hemisphere.
CUBOID or RECTANGULAR PRISM