Reference works are an excellent first stop in your research and are incredibly useful for the following:
- Getting an overview of a topic
- Getting topic ideas for a paper topic or narrowing your topic
- Brainstorming keywords for searching and learning the vocabulary used by authors in that area
- Learning the key works on a given topic
- Discovering the key authors on a given topic
Reference works are a good starting off point, but should not be cited in your research as they are not considered primary or secondary sources. The only exception is when reference works contain primary and secondary sources (like collections of documents and essays).