Descriptors are to ERIC as subject headings are to the library's catalog, i.e. efficient way to search different bibliographic objects that address the same topic. In the library catalog's case this usually means books. In ERIC's, articles, books, dissertations, conference papers, reports, etc.

Generally speaking searching by descriptors is the most efficient way to use ERIC. 

• You ought to be aware that ERIC descriptors have changed over time. This is natural as research objectives change as do the words we use to describe these objectives. For example, the ERIC online database goes back to 1963. But you won't find the descriptor "sexual orientation" in records from that time. Nor would you find "lesbian literature." This doesn't mean there weren't articles addressing those topics, but that they weren't indexed under those headings. You may need to use the Thesaurus of Eric Descriptors and be a bit creative to locate older articles in the database.