Everyone is familiar with finding information, especially factual information. You look for movie times, a restaurant with good reviews, driving directions, who won the gold medal in the men's 100 meter dash in the 1976 Montreal Olympics. It's easy - just put the words into an internet search engine or ask Siri and out comes the answer. Even finding scholarly journal articles for your undergraduate assignments was pretty easy - just type in your topic into "Library One Search" and you have a selection of articles from which to choose your required 5 or 10. The focus here is precision - to get exactly what you want from an authoritative source. You know exactly what you are looking for and you know what tool to use to find it (An app, Google, a library database, etc.)
A literature review is different; in fact, it's the exact opposite. You're being asked to find out what has come before, what research has been conducted, what has been discovered, or how have others solved this problem? There's no set quantity on how much you have to find (it's whatever is "out there"); it could be in books, patents or technical reports, not just journal articles; and there could be many different ways for an author to describe the topic. It's not about finding something - it's about finding everything. For a literature review the focus is on thoroughness.
Precision vs Retrieval
different information needs - different searching techniques.
finding just what you want
finding everything you need
Precision and retrieval are inversely proportional
A high precision search ...
A high retrieval search ...
To solve your information need, you must determine the appropriate balance between precision (quick and easy but likely to miss important documents) and retrieval (gets all important documents but is time consuming and difficult). Have clear goals and a realistic timeframe.
Knowing how to do a thorough literature review is not just "school work". Whether you go into academics or work as a professional engineer, being able to find the necessary information efficiently is a highly desired skill and one that employers expect you to bring with you from college.
Consider this excerpt from Head, Alison J. Learning Curve: How College Graduates Solve Information Problems Once They Join the Workplace. Project Information Literacy Research Report, the Passage Studies. October 16, 2012. p.24
"The employers ... said they expected young hires to be patient but persistent researchers.
Specifically, employers said they needed them to be capable of engaging co-workers in an iterative research process, retrieving information in a variety of formats, identifying patterns in an array of sources, and diving into sources of information.
Yet these information competencies were rarely demonstrated ... [young hires] had a tendency to respond too quickly with answers conveniently plucked from the nearest source. At worst, [young hires] solved information problems with a lightning quick Google search, a scan of the first couple of page of results, and a linear answer finding approach."
Those desired information skills mentioned by employers are the same ones used in high retrieval searching to ensure the necessary thoroughness: iterative research process, variety of formats, array of sources, etc.