Nets

In your book, Maths Mela (Chapter 1), Diksha takes a box, opens it along its edges and lays it flat. The flat shape she gets is called the net of the box. If you fold it back along the fold lines, you get the box again. A box (a cuboid) has 6 rectangle faces, so its net is 6 rectangles joined together.

Every solid with flat faces has a net made of its own faces. The net of a triangular prism has 2 triangles and 3 rectangles: the 3 rectangles in a row fold round into a tube, and a triangle closes each end. The net of a triangular pyramid is 4 triangles: one big triangle with lines joining the middles of its sides makes 4 small triangles, and the three outer ones fold up to meet at a point.

A cylinder can have a net too. It is 2 circles and a rectangle. The rectangle rolls up into the curved face, and the two circles close the ends.

Nitesh cuts a net along its folds and gets 1 pentagon and 5 triangles. One base with triangles all around it is a pyramid, and the base is a pentagon, so the solid is a pentagonal pyramid.