[ocfnash]

It is a Mobius strip.

To convince yourself it might be useful to imagine a point on the surface and imagine tracing it along the strip (avoiding the edges) and seeing if you get back to where your started.

[ioulian]

They've changed the image, quickly, but this was the previous image, which is not a Möbius strip:

https://www.alamy.com/stock-photo-metallic-moebius-strip-iso...

[avip]

Fantastic! They even coloured the faces to emphasize the fact it is NOT, in fact, a Mobius strip.