For vintage or the Topps Heritage sets a master set includes all the different variations (like you have both the red and black backs of 1952 Topps for example). A master set may also be one that includes not just the regular set but all the insert sets (not counting 1/1's of course) as well.
The differences between a Master set and a Basic become dramatic as your collection becomes more modern. For vintage sets, there may be little or no difference due to lack of inserts and far less variations and error cards. For modern sets, there are sometimes 10-15 versions of just 1 player within the same set, and you'll need all of those variations for your master set.
Vintage or modern, the master set also includes all the oddballs and foreign issues too, beyond just the inserts & parallels issued with the more standard companies.
Short answer, it depends on the set. All the above answers are correct, but there can be some interpretation differences between collectors. For example, 2000 Bowman's Best Baseball, my views: Base set - 1-150 (no serial numbered cards) Base 'master' set - 1-200 (includes all rookie card serial numbered to /2999) True 'master set - 1-200 + all insert sets
Others may consider a 'master' set to include 1-150 + all insert sets (ignoring any serial numbered cards).
Other examples: 1971 Topps FB 'base' - all base cards 1971 Topps FB 'master' - all cards, game cards, + posters
2007 Topps Chrome BB - all base cards 'master' 1 - all base cards + japanese variations 'master' 2 - all base cards, japanese variations + Gen Now inserts 'master' 3 - all base cards, japanese variations, Gen Now inserts + auto's Rinse and repeat for refractor
Bottom line, pay attention to what's included in a listing when buying or what's included in the registry for that individual's view of what a 'master' set is.
Comments
D's: 54S,53P,50P,49S,45D+S,44S,43D,41S,40D+S,39D+S,38D+S,37D+S,36S,35D+S,all 16-34's
Q's: 52S,47S,46S,40S,39S,38S,37D+S,36D+S,35D,34D,32D+S
74T: 241,435,610,654 97 Finest silver: 115,135,139,145,310
73T:31,55,61,62,63,64,65,66,67,68,80,152,165,189,213,235,237,257,341,344,377,379,390,422,433,453,480,497,545,554,563,580,606,613,630
95 Ultra GM Sets: Golden Prospects,HR Kings,On-Base Leaders,Power Plus,RBI Kings,Rising Stars
Always buying Bobby Cox inserts. PM me.
I don't consider base set parallels as part of a 'master set'. That would be pretty much impossible for all the new, shiny sets
Base set - 1-150 (no serial numbered cards)
Base 'master' set - 1-200 (includes all rookie card serial numbered to /2999)
True 'master set - 1-200 + all insert sets
Others may consider a 'master' set to include 1-150 + all insert sets (ignoring any serial numbered cards).
Other examples:
1971 Topps FB 'base' - all base cards
1971 Topps FB 'master' - all cards, game cards, + posters
2007 Topps Chrome BB - all base cards
'master' 1 - all base cards + japanese variations
'master' 2 - all base cards, japanese variations + Gen Now inserts
'master' 3 - all base cards, japanese variations, Gen Now inserts + auto's
Rinse and repeat for refractor
Bottom line, pay attention to what's included in a listing when buying or what's included in the registry for that individual's view of what a 'master' set is.