A learning object repository is essentially a digital library that holds learning objects. It is an online location where you can browse or search for learning objects on a particular topic.

A true repository contains learning objects, whereas a 'referatory' provides links to learning objects held elsewhere. However, generally people use the term repository to mean both repositories and refereatories.  

Some repositories are quite broad and contain learning objects useful to a variety of disciplines while others can be very targeted. Read "What are some repositories useful to the Health Sciences?"