Fields
A field is a way to attach a piece of information to a specific asset. You can see all the fields on the right hand side when you're viewing an asset:
You can read more about different types of fields here.
Filters
Filters are a feature that appear when in "All assets" view, and they allow you to select either a folder or field in order to find the right asset(s).
Can I change the order my fields/filters appear in?
Yes, please refer to this article.