Hey Ellane, sorry for the confusion, you're right - notes are saved as .md (markdown) files - it's basically the same, the .md extension tells the program how to read markup formatting. These files can still be read by any text editor!
I've run into the same thing, I was using markdown when I wrote my articles, and then had to remove the formatting when I copied into Medium! I'm looking for ways to make the process easier (importing markdown?), and maybe I'll write a follow-up if I figure it out.
Thanks for reading and for the thoughtful comment! If you come across any interesting features in Obsidian, please share! I'm still learning, I love the program and I think it will only get better with time.