Encyclopedias are a source you can use to get an overview of an unfamiliar subject.
General encyclopedias cover a wide range of knowledge at a very basic level. While they are quite useful for basic fact checking, they are very limited in their depth and usefulness for academic level research.
Subject encyclopedias, on the other hand, provide in-depth, scholarly coverage of a single subject area or discipline. The articles in subject encyclopedias are produced by scholars in the field and usually provide an in-depth bibliography.