Minor patch? Major patch? How to tell?

[Dazusu]

many times with software versions
X.YZ

X changes=major update (big update, adds many new things and many bug fix)
y changes=minor update (medium update, add small things and fixes bugs
z change=bug fixes (small update, fixes bugs)

is what i think

What?

major.minor.build.revision is the general scheme used, at least its how we do it at work, some companies prefer to use the date as a version stamp