AND searches find all of the search terms. For example, searching on Australia AND Church AND History returns only results that contain all three search terms. Very limited results.
OR searches find one term or the other. Searching on Australia OR Church OR History returns all items that contain any of the three search terms. Returns a large number of results.
NOT eliminates items that contain the specified term. Searching on Australia NOT Church returns items that are about Australia, but will specifically NOT return items that contain the word Church. This is a way to fine-tune results.
Your lecturers will often require you to use information from academic journal articles that are peer reviewed (also known as refereed or scholarly journals). Peer reviewed articles are credible sources of information. The articles have been written and reviewed by trusted experts in the field, and represent the best scholarship and research currently available.
A peer reviewed article is an article:
There are multiple ways to identify a "peer-reviewed" article.