Different sources are useful for different purposes. Sources such as blogs and Wikipedia can give you background information and further links but may not be acceptable as a reference to support your assignment. The video below outlines what is meant by scholarly or peer reviewed. If you need to verify that a journal is peer reviewed you can use Ulrich's Periodicals Directory.
The CRAAP test had its origins in the US to help students successfully evaluate and find reliable information. The test has seen many variations but in general if something is CRAAP, that's a good thing!
Wikipedia is a free online encyclopedia which often appears among the top results of any internet-based search. It can be a very useful tool to start your online research but your lecturers and teachers will not accept citations from Wikipedia in your assignments.
How to use Wikipedia
Why shouldn't you cite Wikipedia?