These wave walls use less brick than the same linear-length brick wall. Simple, ingenious and beautiful.
They're called crinkle crankles. How charming. Other names also used are crinkum crankum, sinusoidal, serpentine, ribbon or just wavy wall.
Originally from Ancient Egypt they are mostly known these days to be mostly found in Suffolk, England, which lays claim to about 100 examples.
A single-leaf brick wall over x distance would need buttresses approximately every 1.5-2m, and it would need to be a double-leaf wall if it were a retaining wall.
The crinkle crankle has more strength due to its curved or arched nature, so it can be a single leaf of bricks.
Voila! Not only lovely to look at but efficient as well.
Even Thomas Jefferson incorporated serpentine walls into the architecture of the University of Virginia - and indeed, the image here is not from England, but from there.