Popular Sources: Articles, books, videos, recordings, blog/ social media posts composed for a wide audience. These are sources that tend to be produced quickly with little to no editorial review process. Popular sources can be a place to start--to get a sense for widespread controversy, for example. If you have determined that a source is reliable, a popular source can be a good place to get current information. They can also be used as primary sources for past events.
Academic Sources: Articles, books, lectures, editions, and documentaries written by a scholar for other scholars. These sources have gone through a peer-review process before publication, allowing other experts to ask questions, request adjustments to the argument and evidence, and ultimately provide approval before publication. You can judge the value of an academic source by checking the authority of the author (is this person an expert in the subject?), by tracking the use of evidence through footnotes or endnotes (there should be a lot of these with details about where they got their information), and by following the logic of the argument.