Nothing says 'Romantic By-gone Technology' like a good ol' Airship!
Aerostat: a lighter-than-air vessel (balloon or derigible)
Airship: a power-driven aircraft that is kept buoyant by a body of gas (typically helium, formerly hydrogen) that is lighter than air.
(Note hot-air can also be the 'lifting' gas but can also be used as a means of controlling buoyancy.)
It is a common usage to use the term Airship when referring to Rigid-Airships, often called by the name of the most successful line 'Zeppelins'
Balloon: Commonly a Hot-air Balloon, a large inflated envelope with a suspended gondola for carrying passengers, where the envelope provides enough lift to carry the gondola off the ground.
(Balloons are not steerable or self-propelled, however they usually have a means of heating the air in the envelope-increasing lift, and a means of releasing hot air to decrease lift.)
Blimp: An airship (powered and steerable) with no rigid structure for the gas envelope (Balloon) - Easier to stow and transport on the ground but also limited in size.
Over the years no airships have been as successful as the Zeppelin line, however to this day it is the blimps that persist, and that have had the greatest military successes. (Not that anyone knows about that!)
Dirigible: Literally 'steerable'; a lighter-than-air craft (think net weight vs. lift) which is self propelled and steerable)