This means that diesel will explode if compressed enough. It does not require a spark. Diesels must be fuel injected. They only suck in as much air as they need. To get more power from a diesel usually requires a turbo to push in more air.
Diesels require higher compression than gas engines due to the fuel quality.
Diesels engines are generally noisy due to this high detonation pressure. Diesels are built a lot tougher due to this detonation also. Stronger internal parts, larger oil and coolant capacities,etc. Getting 250,000 miles from a diesel without any repairs is normal. Diesels cannot rev as high as a gas engine due to higher reciprocating mass.