Any kind of shorts that has a "net", or netting, inside it. It can be found in most board shorts.
The netting is used because sometimes, the elastics can show, or the boxer shorts might be longer.
It also holds your junk in place so that it won't fall out of the leg opening or bounce around. It also acts like loose briefs, so you don't have to wear underwear (if preferred).
It feels great to wear my new netted shorts without any underwear!