The simplest way to describe antimatter is in terms of
its behaviour - when particle
and antiparticle meet they annihilate and their mass is turned into energy in the form of g-rays, also called photons.
This process is governed by the second and last equation
you will see this evening, and
surely known to the whole audience - Einstein’s famous equation E=mc2.
Not only is this true for electrons and positrons, it
also occurs for quarks and anti-quarks
and more complicated objects like protons and anti-protons. You would also be in trouble if you met your
anti-you.
However this possibility is still someway off; it was
not until 1996 that anti-hydrogen,
the simplest anti-atom was produced.