We're talking about two separate things here:
1. The Windows program that can open the database.
2. The file that contains the database itself.

1. This can be either retail Access or runtime Access.

You need to pay M$ for every copy of retail Access that you install on PC's. This retail version can create, open, and modify databases.

If you pay M$ for one copy of ODE Tools, you can then install runtime Access on an unlimited number of PC's. This runtime version can open databases.

2. This can be either an mdb or mde file.

An mdb can be created, modified, objects can be imported and exported, IF you have retail Access installed.

An mdb can be opened with either retail or runtime Access.

The mde can be created from an existing mdb IF you have retail Access
installed.

The mde can be opened with either retail or runtime Access.