When you evaluate your sources, you are asking yourself many different questions. Is this source appropriate to my needs? Is this source accurate? Does it have a particular bias? Do I need something current or historical? Do I need broad information or something very specific? Scholarly or popular sources?
Both the library and the web contain many useful sources, and also many sources that are not appropriate to your research needs.
What types of sources do you need? Books, articles, newspapers, websites? It depends on what type of research you're doing.
Scholarly Articles: Written by and for an expert audience. Also frequently called "peer-reviewed" publications.
Popular Articles: Written by journalists for a general readership.
Both can be valuable, depending on your need.
Primary Sources are first-hand accounts of events, topics, historical periods. Some examples include diaries, speeches, photographs, articles reporting original research, and most newspaper articles.
Secondary Sources interpret, critique, or analyze primary sources. Some examples include textbooks, essays or reviews, some newspaper articles, and encyclopedias.
Many publications operate from a particular political stance or bias, though this can change over time due to editorial leadership. This bias can impact how or if an event is reported.
Ad Fontes Media Bias Chart (as of August 2022)