What is the difference between GIFs and MOL files?
 
Chemical structures are stored in IDdb both as MOL files and as GIFs.

The GIF is simply a picture of the structure, and it can be viewed in a web browser without any need for a plug-in.

The MOL file is a chemically-meaningful file format. This is the file that is searched during a structure search. It can also be copied and pasted into other chemical structure applications. Web browsers cannot ordinarily display MOL files, and therefore the Chime Pro plug-in is required to view the MOL file.

By default, structures in IDdb display in GIF format. To view a MOL file, click on the View Molfile link alongside the structure.