The document introduces different 2D shapes, with each shape stating the number of its sides and giving a clue to its identity. The shapes included are a circle with 1 side, a semicircle with 2 sides, a triangle with 3 sides, a square with 4 sides, a pentagon with 5 sides, a hexagon with 6 sides, a heptagon with 7 sides, an octagon with 8 sides, a nonagon with 9 sides, and a decagon with 10 sides.