Thanks, yes, its for school =)sure sounds like a homework question to me
symmetric is when both sides know and use the same password or key to secure a connection.
asymmetric means each side uses a different password or key to secure a connection.
hashing is simply a way to "fingerprint" a file for identification purposes mainly, and in no way is it a suitable way to secure a connection.
with this in mind think about all you do with and around your pc and it should be pretty obvious a couple examples of each.