A non-orientable surface is a type of surface that does not have a consistent "side." This means that if you travel along the surface, you can end up on the opposite side without crossing an edge. A common example of a non-orientable surface is the Möbius strip, which has only one side and one edge. In contrast to orientable surfaces, like a sphere or a cube, non-orientable surfaces challenge our understanding of dimensions and geometry. They are important in various fields, including topology, which studies the properties of space that are preserved under continuous transformations.