Searching, especially when using bibliographic databases, can be a complex task as so many journal articles and other items are indexed. Structuring your search using Boolean terms "AND", "OR" and "NOT" will be particularly helpful, e.g. (Students OR undergraduates) AND (impact OR effect OR implications) AND Covid-19.
Other options are also in common use though.
Looking for a specific item?
Use the author's surname and the whole title, or one or more words from the title. For example, Saunders research methods
Searching for items on a topic?
Enter the key words defining the topic, e.g. business research methods
Looking for a set phrase?
Use quotation marks to search for an exact term, e.g. "primary school"
Not sure about the spelling?
Check the database or other site to see which symbols, if any, can be used as wildcards. If supported, you can simultaneously search different spellings of a word.
For example, in EBSCOhost databases, wom?n will generate results for woman and women (one letter difference); lab#r for labor and labour (multiple letters are possibly different).
Some bibliographic databases, e.g. CINAHL offer the option of searching a controlled vocabulary - thesaurus searching. This option is often recommended when running systematic reviews as there is greater consistency in the search application. The terminology for this can differ - look for subject headings, MESH (medical subject headings), thesaurus, or similar.
Also consider if any criteria should be used to restrict or refine your search.
Are you looking for items:
Many of the searching platforms let you select such criteria before you run your search.
Sometimes though, you will only apply these when you start reviewing the results generated by your search.