Educate Me On Bipolar Disorder

Edit*

My husband and I have been having issues for a few years. Saturday we got into a horrible argument and almost called it quits. I don't bring family into our problems but I called his mom this time. She informed me that he was diagnosed with bipolar disorder as a teen and I don't know why no one told me anything about that until now. My husband thinks he's 'fine' and outgrew it and doesn't need medicine. He is not fine. I wondered last year about him having bipolar disorder because he goes thru phases where he literally acts depressed and won't do anything but claims he's fine. Now I know. I'm going to talk to him about seeing someone to get medicine again but in the meantime, can some please educate me a little on this condition? Do you have a spouse with bipolar? The lows last forever it seems and I don't know how to deal with them most of all. Thank you in advance.

* I hate knowing that I've said some very cruel things to him over things he can't help. Now that I know. And I hope that I can find advice on how to say helpful supporting things instead.