The following is a comparison between football and network emulation.
Just as the crowd is squeezed through a few stadium entrances, packets are restricted to the link bandwidth.
Waiting in line at the concession stand is like packets sitting in queues waiting to get processed.
Defense is the ultimate impairment since their goal is to stop the offense (application). A sack is like packet loss and even forward achieving running and passing plays act like delay and jitter.
A touchdown is when the application completes its task.