Material flagged as "Adobe DRM EPUB" will continue to have DRM after the download via ADE. In fact, you download an ACSM file which acts as a "ticket" that when processed via ADE allows the download of the ADE file. With the DRM in place you can only read that file on another device that has been authorized with the same ADE key as your PC (and even then, only by an application that supports ADE DRM).
On the other hand, an "EPUB (DRM Free)" can be read by any application than supports EPUB format.
If you google "Apprentice Alf" you might learn of tools that allow the conversion of "Adobe DRM EPUB" protected files to "EPUB (DRM Free)" files.