This video describes what top level domains are and what they mean. Top level domains are the .com, .org., .edu (etc) part of a website. This can tell you a lot about the information being shared and by whom. But there is an assumption that a .org website is more credible than a .com website -- that's just not true because anyone can purchase or sign up for a .com or .org. You need to evaluate all the information you come across and make no assumptions about trustworthiness until you've done the work. Check out the evaluation techniques on this research guide (especially the SIFT and CRAAP methods) for help with evaluating websites.
Top-Level Domains from Imagine Easy Solutions on Vimeo.