Most topics need to be broken down into smaller chunks by identifying two or three main concepts. Once you have each main concept, think of synonyms, broader, narrower, and related terms. Check the database thesaurus, if there is one, to help you determine some of these terms.
Boolean operators help you tell the database how to combine your main concepts and search terms:
These are articles written by people considered to be experts in their fields. They spend years conducting experiments, reviewing other literature on the topic, and writing their article. It often goes through a very intense review process to make sure the information is objective and accurate. It can often take a year or two for it to be published.
Nothing - all three are just different names for the same idea.
Here are some things to look for in order to determine if an article is scholarly:
Many of the library databases allow you to limit your search results to journals that are scholarly, academic and/or peer reviewed. That does not mean that you will only get scholarly articles though as these types of journals will also publish items such as letters to the editor or book reviews. You want to review the articles that come back and make sure they meet the qualifications.