Vbytes is a more recent estimation that still counts in bytes, but does not count the bytes of certain parts of the transaction such as the witness data (IIRC).
It does.
Virtual size is transaction weight divided by 4 and weight is counting witness by computing "base size" (which is serialized size without witness) multiplied by 3 added to the "total size" (which is serialized size with witness).
nope
bytes are actual real bytes of the full transaction
then
vbytes change this using cludgy code to give:
a. the entire legacy transaction a 4x meaning its total size is not in bytes but 'weight' of 4x of bytes
b. segwit get multiplied differently