Switch a switch steps up on a bridge in that it has multiple ports. When a
packet comes through a switch it is read to determine which computer to send
the data to. I.E. one computer will be the sole receiver of the package.
This leads to increased efficiency in that packets are not going to computers
that do not require them.
Now the email analogy has multiple people able to send email to multiple
users. The switch can decide where to send the mail based on the address.
Most large networks use switches rather than hubs to connect computers within
the same subnet.