"Version" CFBundleShortVersionString (String - iOS, OS X) specifies the release version number of the bundle, which identifies a released iteration of the app. The release version number is a string comprised of three period-separated integers.
"Build" CFBundleVersion (String - iOS, OS X) specifies the build version number of the bundle, which identifies an iteration (released or unreleased) of the bundle. The build version number should be a string comprised of three non-negative, period-separated integers with the first integer being greater than zero. The string should only contain numeric (0-9) and period (.) characters. Leading zeros are truncated from each integer and will be ignored (that is, 1.02.3 is equivalent to 1.2.3). This key is not localizable.
CFBundleVersion -- is identify the last and current build available in itunes conncet, if you use in the legal, the appstore doesnot accept/reject your app, may be the binary also not uploaded.
you can see the type in your info.plist
<key>CFBundleVersion</key> <string>1.0</string> <key>CFBundleShortVersionString</key> <string>1.0</string>