Question

What does an unabridged dictionary provide?

Answer 1

I can think of three things that an unabridged dictionary could provide:
1.A whole load of extra words you never knew exist(ed) and will probably never need (unless you play Scrabble*).
2.Extra details like the origin of words (etymology) as far back as they can manage to find in print, nevertheless mostly on guesses.
3.Volumes are bound to fill an otherwise empty bookshelf and it looks good. (Gaud, there must be another word for that...)

Answer 2

An unabridged dictionary is a complete dictionary. Unabridged is defined as a complete or not shortened. Therefore, an unabridged dictionary will include more obscure, less used words that an abridged (or shortened) dictionary would not. For the most part an abridged dictionary will suit your needs unless you need to know a specific, obscure word or perhaps if you play Scrabble.