Matchstick puzzles are rearrangement puzzles in which a number of matchsticks are arranged as squares, rectangles or triangles. The problem to solve is usually formulated as: "move n matchsticks to make m squares (or triangles, or rectangles, or circles)".
However some of the puzzles require lateral thinking and are not just about making geometric shapes.
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Matchstick puzzle Wikipedia(Text) CC BY-SA