Would someone explain to me gender neutral pronoun thing?

I dropped my son off to a small private college in California 2 weeks ago. At least 10 people spoke to us and told us up front that they relate to he/she, they/them or the like. I don’t have a problem with this at all but I would like to understand it better and learn how to address them properly. I’m still a little confused even after trying to Google it.

Young adults/Millennials will explain what pronoun they’d like someone to use when referring to them. There are various pronouns and each person picks the one they want. You can’t know ahead of time but 1° if you try it’ll be appreciated 2° many Millennials understand that it’s harder to get used to for “old folks” like us.
Think of it as this generation’s "Negro"vs. “Black” vs. “African American” word battle. At some point, I assume some pronouns will be preferred by a majority and will be used, while others won’t stay… or perhaps the right to all kinds of different pronouns will remain.

There is already a long thread on the subject: http://talk.collegeconfidential.com/parents-forum/1924230-pronoun-mess-in-ann-arbor.html#latest