Library guides, librarians, databases, and literature experts use a lot of terms that may be unfamiliar or that need clarification. Here's a list to help with that.
Periodical is a broad term meaning anything that is published periodically, i.e. on a regular or semi-regular basis. It could refer to newspapers, magazines, newsletters or journals.
Serial is also a broad term meaning anything that is published "in a series," i.e. with incrementally numbered issues. It is most often used to mean academic journals.
Journals are publications that come out on a regular basis and that contain articles, quite often with scholarly content, but not always. Look for Peer-Reviewed content to use in assignments and papers.
Peer-Reviewed or Refereed: content that has been subject to an evaluation and approval process by experts in the same field as the writer. Most databases will allow you to filter results to find exclusively articles that are peer-reviewed, but if you want to further check the status of a journal, look up the title in Ulrichsweb, a service that rates periodicals for scholarly content (a little referee jacket means that the journal is refereed, aka peer-reviewed).
Dictionary: reference book that lists words in order—usually, for Western languages, alphabetical—and gives their meanings; basically, a set of words with information about them. In addition to its basic function of defining words, a dictionary may provide information about their pronunciation, grammatical forms and functions, etymologies, syntactic peculiarities, variant spellings, and antonyms.
Encyclopedia: reference work that contains information on all branches of knowledge or that treats a particular branch of knowledge in a comprehensive manner. Most people think of an encyclopedia as a multivolume compendium of all available knowledge, complete with maps and a detailed index, as well as numerous additions such as bibliographies, illustrations, lists of abbreviations, etc. An encyclopedia is essentially a more in-depth dictionary.
Glossary: A short list of words used in a book, usually in its appendix, with definitions; a partial dictionary.
Concordance: an alphabetical arrangement of the principal words in a book, with citations of the passages in which they occur. A very limited index.
Index: a comprehensive sequence of access points to all the information contained in a text, grouped by larger contexts and topics, and including cross-referencing, subheadings, synonymous terms, etc. An index is a more detailed and thorough concordance.
Anthology: Any published collection of writings, typically by various authors, and representing the best or most noteworthy examples of their type.
This Information Tools libguide has a lot of helpful links that further explain these terms, and that provide sources for book reviews, biographies, quotation dictionaries, and much more.
(definitions taken from the Oxford English Dictionary, Britannica Encyclopedia, and my own brain)