Whether a major or a minor  version, every version  is a full  copy of the
file. There are no deltas.

It is a FULL version, whether minor  or major.

Somewhere I read that the minor  versions are drafts and the major
versions are actually revisions. Could someone explain if this is
what is being discussed?

When you turn on versioning  you have a choice of either using just
simple numbers 1,2,3,etc or Major and minor  versioning where the numbers
are 1.1, 1.2, 1.3, 2.0 etc. If the site is a publishing site then the
approval process uses Major/Minor versioning automatically and treats
Minor versions  as drafts and Major versions as published documents
awaiting approval. Checking in a Minor version  won't start the approval
process automatically, but Publishing a Major version will. The
confusion is that you can use major/minor versioning with or without
using publishing. When used with publishing there is additional
terminology that goes with the versions like draft, published, revision,
etc.