Metadata views allow you to choose one or more metadata fields and form them into views of that metadata.
As an example, your assets might have 20 different fields of metadata to describe them. But for a certain User Group you might only require them to see 5 of those fields.
You can create a Metadata View that just has 5 of those fields, and then when those users see the assets they can use that metadata group and only see the 5 fields. The metadata still exists but is hidden to them.
But a different group of users might require to see all 20 or a different subset of those fields, another Metadata View could be created for showing those fields for that other group of user.
Likewise, you might require that when searching and using the search filters only certain fields are shown or made available to the search, you can create a Metadata View that is used for search.
Each Metadata View is comprised of Metadata Fields. It's best to create the fields first, and then map those into views.