whats the diff between diesel gas and regular gas?

They are both solutions of different hydrocarbons. The difference is they contain different hydrocarbons. Gasoline generally contains hyrdrocarbons containing 6-12 carbon atoms, while diesel fuel contains hydrocarbons containing 13-18 carbon atoms.

Octane rating: Octane rating is a representation of a gasoline's ability to resist detonation. Some time back if the 20s or 30s, the oil industry standardised the way they rated they measured gasoline's ability to resist detonation. A large number of fuels were burned in a test engine. The fuel found with the lowest detonation resistance was n-heptane (C7H16), and the fuel with the highest detonation resistance was found to be octane, or more correctly, Iso-octane (2,2,4 trimethyl pentane). Heptane was given an octane rating of 0, and iso-octane got a rating of 100. All the other fuels were rated by comparison to a known mixture of iso-octane and heptane. A fuel with the detonation resistance the same as a mixture of 75% iso-octane and 25% heptane was given an octane rating of 75.

Later we've found fuels with detonation resistance much better than that of pure iso-octane.

octane ratings of some common fuels:
n-octane: -20
heptane: 0
pentane: 60
2,2,4-trimethyl pentane(iso-octane): 100
ethanol: 105
methanol: 105
benzene: 105
methly tert-butyl ether: 115
ethyltert-butyl ether: 118