In the linked pdf, a bight is bend/curve of rope that doesn't cross itself; however, they show a "double bight" which seems to cross itself. They say that the "strands" don't cross... errr ok?, I'm not understanding how the "double bight" is not a "loop"... the rope is crossing itself!
You "make" a loop but "take" a bight, as unhelpful as that may be. A loop is a step in making a knot, where as a bight is just a handful of rope somewhere in the middle of it.
You can tie a regular bowline, or a bowline on a bight. The same knot will need a different technique for tying on a bight, since you can't pass the ends through. When you tie a bowline on a bight, first you take a bight, then you make a loop.
A "bight" is simply a curved section in the middle of a line. There's no hard and fast definition of "how curved". Some folks would say a "bight" can't be any more than a semi-circle, others would say it can loop around as many times as you want.
https://home.army.mil/wood/application/files/8915/3868/3675/...
In the linked pdf, a bight is bend/curve of rope that doesn't cross itself; however, they show a "double bight" which seems to cross itself. They say that the "strands" don't cross... errr ok?, I'm not understanding how the "double bight" is not a "loop"... the rope is crossing itself!