Subject databases allow you to carry out a strategic search for journal articles. You can search using a combination of search terms, filter and narrow results (by date or subject area for example) and save your searches. There is some overlap between the databases but every database also has unique content. Help guides are available within the Discover record for individual databases.
To make sure that your search strategy is consistent across all the databases you are using, you will need to understand any differences that exist to how they each apply Boolean operators, adjacency (or proximity operators) and search symbols such as truncation, wildcard and phrase searching. You can find this information in the help section of the individual databases you are using. You can also use this handy database syntax guide that pulls together this information for most of the major databases.