Drive API:What is the difference between size and quotaBytesUsed in Drive API

[Vedhasree]

For the documents in drive i can see size and quotaBytesUsed values are same even in case of multiple versions of a file.Could you let us know the scenario in which there will be different values for these 2 fields?

[StephenHind]

@Vedhasree size is the size of the file that you can see any for any file including files you do not own. quotaBytesUsed is the amount of your own quota that's used, so if it's not a file that you own then it isn't using your quota, so quotaBytesUsed should empty or 0 but you will still be able to see the size.

[Vedhasree]

@StephenHind Even in case of files which is not owned by me(Shared with me by some one) ,I see both size and quotaBytesUsed are same.