You can probably use it to do similar things, but it’s a different format. Everything exists in one place, so you’re not using it to open and save files externally (but you might be able to export individual pages as markdown).
For example, this post today is announcing that they have implemented collaboration. Until now, people would have been using it individually for personal notes and project management.
The main function I like is being able to make objects with custom fields, which I can then add information to and sort. I haven’t used it extensively yet, but I have friends that use Notion for quite a bit