A multiplicity is a lot of something, usually countable and varied. If you're skilled in juggling, tightrope walking, and lion taming, you could call yourself a circus performer with a multiplicity of talents.
Having a multiplicity of something is more than just having a lot of it. You may have a big pile of white tube socks, but that wouldn't qualify as a multiplicity. You'd have a multiplicity of socks if you've got not just the white tube socks, but striped knee socks for soccer, black silk socks to wear with your tuxedo, wool hiking socks, low tennis socks with pom-poms on the back, and socks with little pockets for your toes.
