These nets of 3d shapes are for the 5 platonic solids, as illustrated below. Each face is a regular polygon. A regular polygon is where each edge is the same length (equilateral), and the angle between each joining edge is the same (equiangular).
Click on the 3d shape you want to make and follow the instructions for printing. Printing on card works best as it gives the shape rigidity, but paper will work too. Cut the shape out along the outside edge, and then score along the inside lines. Make into a 3d shape, tucking the tabs in, and secure using glue or sticky tape.