The Primary Development line of D&D:
Original D&D
=>
Supplement I: Greyhawk (Very important supplement; added Thief, Paladin, Ability Scores that Matter; variable hit dice, XP awards, etc.)
=>
further Supplements (Blackmoor & Eldritch Wizardry), and The Strategic Review/The Dragon magazines (more new classes, incl. Bard, first "prestige" class)
=>
AD&D 1st edition (gathers together OD&D+Supplements)
=>
Unearthed Arcana (most significant addition: Weapon Specialisation. Most other changes discarded).
=>
Oriental Adventures; Dungeoneer's Survival Guide; Wilderness Survival Guide (significant addition: Non Weapon Proficiencies. Later to become Feats (e.g. Blindfight) and Skills (e.g. Ride))
=>
AD&D 2nd Edition (gathers together AD&D+Supplements, some revisions to make mechanics clearer)
=>
"Complete" Books (major addition: kits, and the variability of PC abilities. This would be revised...)
=>
Player's Option (major additions: strict miniatures rules; very customisable characters; skill points so skills could improve each level; levels of weapon specialisation (influenced by BECM D&D); some attempt at game balance)
=>
D&D 3rd edition (revamping, but many elements based on previous editions, especially PO, or adapted from other systems based on previous editions).
=>
D&D 3.5e (fixing broken things; making PC monsters more feasible)
The Secondary Development Line:
OD&D
=>
Supplement I, Greyhawk
=>
Basic Edition (Eric Holmes) (influenced by AD&D)
The Tertiary Development Line:
OD&D
=>
Supplements (some elements of Basic/Holmes)
=>
Basic Edition (Moldvay) + Expert Edition (Cook) - a radical revisioning of D&D. Elf, Dwarf and Halfling as classes; a new ability score system
=>
BECM Edition/Cyclopedia (Mentzer) - adding new systems, a very complex weapon mastery system at upper levels, a skill/proficiency system (influenced by DSG & WSG)
Cheers!
Original D&D
=>
Supplement I: Greyhawk (Very important supplement; added Thief, Paladin, Ability Scores that Matter; variable hit dice, XP awards, etc.)
=>
further Supplements (Blackmoor & Eldritch Wizardry), and The Strategic Review/The Dragon magazines (more new classes, incl. Bard, first "prestige" class)
=>
AD&D 1st edition (gathers together OD&D+Supplements)
=>
Unearthed Arcana (most significant addition: Weapon Specialisation. Most other changes discarded).
=>
Oriental Adventures; Dungeoneer's Survival Guide; Wilderness Survival Guide (significant addition: Non Weapon Proficiencies. Later to become Feats (e.g. Blindfight) and Skills (e.g. Ride))
=>
AD&D 2nd Edition (gathers together AD&D+Supplements, some revisions to make mechanics clearer)
=>
"Complete" Books (major addition: kits, and the variability of PC abilities. This would be revised...)
=>
Player's Option (major additions: strict miniatures rules; very customisable characters; skill points so skills could improve each level; levels of weapon specialisation (influenced by BECM D&D); some attempt at game balance)
=>
D&D 3rd edition (revamping, but many elements based on previous editions, especially PO, or adapted from other systems based on previous editions).
=>
D&D 3.5e (fixing broken things; making PC monsters more feasible)
The Secondary Development Line:
OD&D
=>
Supplement I, Greyhawk
=>
Basic Edition (Eric Holmes) (influenced by AD&D)
The Tertiary Development Line:
OD&D
=>
Supplements (some elements of Basic/Holmes)
=>
Basic Edition (Moldvay) + Expert Edition (Cook) - a radical revisioning of D&D. Elf, Dwarf and Halfling as classes; a new ability score system
=>
BECM Edition/Cyclopedia (Mentzer) - adding new systems, a very complex weapon mastery system at upper levels, a skill/proficiency system (influenced by DSG & WSG)
Cheers!