Short answers, pulled from the story.
The Hindenburg, the hydrogen-filled German airship LZ 129, burst into flames while approaching its mooring mast at Lakehurst, New Jersey on the 6th of May 1937. Of the 97 people aboard, 35 died: 13 passengers, 22 aircrew, and one American ground crewman. The disaster was filmed and broadcast live by a radio reporter, ending public confidence in passenger airships.
Hydrogen was used because it provides the highest lifting force at 1.1 kilograms per cubic meter and was inexpensive and readily available. Helium is non-flammable but gives slightly lower lift at 1.02 kilograms per cubic meter, and for many years significant supplies existed only in the United States, making it scarce and expensive for international operators.
Henri Giffard made the first engine-powered airship flight in 1852, flying 27 kilometers in a steam-powered airship. The first fully controllable free flight followed in 1884, when Charles Renard and Arthur Constantin Krebs flew La France, an electric-powered airship that covered 8 kilometers in 23 minutes and landed at its departure point.
U.S. Navy blimps patrolled coastal convoys and drove German and Japanese submarines underwater, preventing attacks on shipping. Of more than 89,000 ships escorted by blimps, only one was sunk by a submarine. Between 1942 and 1945, Goodyear built 154 airships for the Navy, and the airship personnel force grew from 430 to 12,400.
On the 19th of October 1901, Alberto Santos-Dumont flew his airship Number 6 from the Parc Saint Cloud to the Eiffel Tower and back in under thirty minutes. The feat won him the Deutsch de la Meurthe prize of 100,000 francs and inspired many other airship pioneers.
A dirigible is any powered, steerable balloon; blimps and zeppelins are subtypes. A blimp is a non-rigid airship that relies entirely on internal gas pressure to hold its shape. A zeppelin is a rigid airship with an outer structural framework enclosing internal gas cells, a design pioneered by Count Ferdinand von Zeppelin and built primarily by his company, Luftschiffbau Zeppelin.