If the question was 'how does a gaming packet look different than a file transfer packet?'
Then I would answer file transfer packets tend to be the max size you network allows (MTU) and are sent 'heel to toe' using a windowing protocol based on TCP, while gaming packets are shorter, often UDP, have a processing time between them, and are ACKed individually.
It should not be impossible to guess which are which, rapidly.
I tried to remain child-like, all I acheived was childish.