Fighters were like 1e fighters
Magic Users were 1e magic-users, the could not specialize and were restricted to dagger only (optional weapons were available)
Clerics were like 1e clerics, but got spells starting at 2nd level and didn't get bonus spells.
Thieves were like 1e thieves, but Find and Remove Traps were seperate skills, Read languages was a flat 80% at 4th level, and they had d4 HD
I'm not sure about the Gazetteer Classes, but Paladin, Knight Druid and Avenger (the original Blackguard) were basically prestige classes. (Like bard in 1e).
Paladin: lvl 9 lawful fighter, sworn to Lawful Church. - Minor cleric spells and turn undead (I think), detect evil
Knight: lvl 9 Neutral fighter, sworn to lord of the land - Land, shelter in kingdom, etc
Avenger: lvl 9 chaotic fighter, loose alliance with chaotic church - most the same powers as a paladin
Druid: lvl 9 neutral cleric, trained under another druid. - Spell spell list, no metal weapons/armor, no turn undead. No shapeshifting.
Mystics were AD&D style monks, limited to 16th level of advancement. Powerful suckers though.
Dwarves were fighters with better saves, trap detection, infravision.
Elves were fighter/mages, limited to 5th level spells. Could cast in armor. Infravision and secret doors.
Halflings were fighters, but had benefits for being small (bonus to hit, AC, initiative) and hide in woodlands (90% chance, IIRC) but used a d6 hd and had to use small or medium weapons
The conversion area discussed the posssiblity of race/class combos and gnomes as a PC class.
BTW: I heard there was a bard and ranger class in Dragon for Basic/OD&D. Is this true? What issue was it? (so as to find them in My Dragon Archive)