Bipolar 2 is a tricky diagnosis. People with bipolar 2 have depressive episodes that can vary in severity and also hypomanic episodes. Unlike bipolar 1, they do not have severe manic episodes. A lot of people are initially diagnosed with depression or with anxiety disorders, or both, or with ADHD, and only later diagnosed with Bipolar 2. This can very naturally happen when someone initially seeks treatment while in a depressive phase, the obvious diagnosis is depression. A careful history might bring up the question of Bipolar 1 or 2, but even then the provider might need to see a manic or hypomanic phase to make a diagnosis. People with bipolar 2 are more likely to realize something is wrong and seek help during a depressive phase, as hypomanic phases are often less problematic. If they do initially seek treatment during a hypomanic phase, they may get diagnosed with ADHD or anxiety if the provider doesn't know about the depression. Even once a provider knows a patient better and has perhaps seen some ups and downs, hypomania can be hard to identify. It can feel good- you might not really think it is a problem, and if it's not a problem, why bother? Or there are some problems, like being really easily distracted, not being able to focus or complete things, or spending a bit too much, but it still feels good, and so in the moment you don't really care about the things that might cause problems for later. So you might not be talking with your provider about how these behaviors change. And unlike mania, hypomania is not easily noticed by people around you, especially not in shorter interactions. It often looks like you are just happy or excited. So it really requires knowing someone well, paying attention to detail, and a pattern of behavior to recognize a hypomanic episode in someone else. If you are looking for it- because you know there is a history or them or a diagnosis of bipolar 1 or 2, then you have a better chance. But if you aren't looking for hypomanic episodes, you might miss them entirely, or notice but diagnose anxiety or ADHD, which can have some of the same symptoms. It probably goes the other way as well, if someone comes to a provider with a diagnosis of bipolar, things might get called hypomania that are actually something else. If you are looking too hard for it, every time someone is happy you are suspicious. And things like ADHD or anxiety could be missed and not treated because they are being called hypomania. So then you just get a frustrating mix of different diagnoses that it seems like are constantly changing.

Again I wrote too much and have to split into two posts.
There is a difference, and you and your doctor knowing which you have can be helpful for finding the best meds (if you decide to go with meds) and also just for framing what is happening and understanding better. But in other ways it doesn't matter. For meds, they can give you the same meds for either, but they might get to the right med or right combo more quickly with the correct diagnosis. For understanding, personally or for therapy, or for talking to friends and family, the symptoms are more important than the name. And name can give you a tool to understand or explain, but you have to go deeper one way or another.
Depression is what we think it is, it sounds like there is no questions about whether you have some sort of depression or depressive episodes. Depression can get better or worse, be anywhere from extremely severe to mild, can be long lasting or shorter, can happen once and never again or repeatedly, and can swing up and down. But the swings in depression never go to overly happy. You might alternate between depressed and not depressed, or between a little depressed and a lot depressed, or between a lot, medium, a little, and not depressed at all, or any variation of that. But you don't swing into the upper ranges of mood- the mania and hypomania. You might be happy sometimes, or excited, or all sorts of good emotions, but in a way that generally makes sense for the situation, rather than a general over the top happy/frantic.

There just names a doctor can put on for insurance. I wouldn't worry about it. Look both of them up and determine yourself which best suits you. Then talk to your doctor.

My diagnosis from the mid 1990s changed from schizoaffective disorder to bipolar disorder about five years ago. Also read some where that there is some flavor of bipolar with a schizoaffective component.

From what I understand people with bipolar have higher highs and lower lows than those who suffer from the traditional symptoms of depression. But I'm not 100% positive.