How do I get a personal color diagnosis?

People have been talking about personal color for a while now, but I have absolutely no idea what it is.

Why do I need to get a personal color analysis? I find this difficult. I don't even know what my personal color is. Also, there are so many different types of personal colors; it's such a hard problem.

Can I get a personal color analysis at home?

Please let me know if you know. Also, please explain why, when personal color diagnosis and classification began, and why cosmetics should be selected accordingly.

I just want to buy something without worrying about all this, but it's difficult.

Is it absolutely forbidden to just use it carelessly?