Starting with, I am not two-spirit, I just know some people who are.

So, here are some random points

At one point it was used to describe, in English, non-euro-centric gender roles that exist within many of the Canadian First Nation tribes. Previous words (often used by non-native people) to describe those roles would often just be slurs. It's one term to try to describe something in many different cultures. It is an English-Language term, not a traditional native one.

There are hundreds of recognised tribes in North America, with many different belief systems and cultures. Trying to lump them together as one is kinda like saying the ever country in Europe is the same. So, the term is kinda hard to pin down, and it also doesn't apply to every tribe.

It very-specifically does not mean that you have the spirit of a woman and the spirit of a man.

Its meaning has expanded, and I've seen it used catch-all for LGBTQ+ by native people, often as a way to reject the idea that they need to fit into euro-centric cultural boxes. I also know that some people refuse to use it, because they feel it's something that is sometimes pushed onto them by outside sources (aka, well-intentioned white people), or it doesn't really fit into the historic cultural beliefs of the tribe they are from, or they just don't want to use it.
(see also "Native American" vs "First Nations" vs "Indian")

Something important: It is not an identity you can have if you are not from one of the tribes who lands are within the current Canadian or United States boarders.