AND finds records with all of your terms/keywords and narrows your search.
OR finds records with any of the terms and broadens your search.
Truncation finds records with a term's various endings. For example, nurs* = nurse, nurses, nursing, nursed, etc.
Quotation marks search for a phrase instead of individual words. For example, "social media".
For both these resources, you can expand your results by also searching in the title for the phrases scoping review or meta analysis.