"The Loop with No Inside or Outside"
Take a strip of paper, give it a half-twist, and tape the ends together. You have created a magic object. If you draw a line along the inside, you will eventually reach the outside without lifting your pen. It has only one side and one edge. This is the Möbius Strip.
The Möbius Strip is a key object in Topology, a field of math that studies properties preserved under continuous deformation (stretching, twisting, but not tearing). To a topologist, a coffee mug and a donut are the same because they both have one hole.
Due to its endless, cyclic nature, the Möbius strip inspired the universal recycling symbol (♻️). It is also a popular symbol for infinity and eternal love in art and jewelry.