@hayleyturner According to what I've read, bipolar I is when you've had at least one manic episode ("high") that was so severe it lasted at least a week, or it meant you couldn't function normally, or you weren't able to tell what's real, or you had to be hospitalized. If you have bipolar disorder but you've never had a manic episode as severe as that, then it's bipolar II. But I'm not an expert and it's very complicated.
Both bipolar I and bipolar II are severe disorders that are difficult to diagnose because they can be similar to other disorders, or the symptoms can be caused by other things. This means a diagnosis has to be made by a psychiatrist who has carefully considered all the facts of your particular case.
There's plenty of information about bipolar disorder on the Internet, although a lot of it is confusing. For example, see: Everything You Need to Know About Bipolar Disorder
Charlie