Tears are made by the two lacrimal glands and their purpose is to clean the cornea.  The tears that you aren't busy whiping up with tissues drain into the tear duct openings (punctum). Then they go into a lacrimal sac and eventually to the nose, which is why your nose gets runny when you cry.  They are salty and contain lysozyme, which kills bacteria, helping to  reduce eye infections.  Tears coat your eye each time you blink.   So now you know that it really is okay to cry, in fact, it's necessary!