Tessellation Symmetry:
Glide (Slide / Translation)
with Reflection (Flip)

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Take a look at the red shapes in this tessellation. The "tile" is a tropical reef fish. We make this kind of tessellation by copying the tile over and over again, and then doing translation/slide/glide for the ones in the same row as the original fish.

Then, we flipped (reflected) half of them left-for-right or top-for-bottom or something like that, and fitting all the tiles together. Also, this fish tessellation does a little translation (sliding): After it's copied, each fish moves a little down and a lot to the left.

So, it's fair to say that this tessellation uses two types of movement: Reflection / Flip, together with Translation / Slide / Glide. The pros usually call this a "Glide-Reflection".

Now look at this "horsemen" tessellation by M. C. Escher in 1946. Can you see which horses are just translated (slid) and which are reflected and then slid?

Click on the button called "next page", below, to see one more kind of tessellation symmetry.