Adding extra information to a sentence (or paragraph) using brackets, dashes or commas. If you take it out again, the passage should still make grammatical sense. "The case was worn - and very full - ...
When you're at an airport and see propeller aircraft, you likely think it is powered by a piston engine. This is usually true among smaller planes, like the Cessa 172 Skyhawk and the Piper Archer, or ...