Is there a name for data structures with a table of contents?

I'm writing a blog post about serialization formats with bounded and unbounded traversal.

My unbounded example is JSON, where you have to parse each piece to find its end.

The simplest bounded example is a zip file, where you read the table of contents at the end, and can immediately find the offset of any particular file.

I'm describing why it's 'faster' to read one particular file inside zip vs JSON.

Is there a name for this?