Pro Tip: You can also type in your search term followed by site:.[domain name here] to control which kinds of websites you will see.
Example: "gilded age" site:.edu will only show you ".edu" websites. If you typed in site:.org instead, you'd get ".org" sites and so on.
Credit: LifeHack.org
If it ends in:
.gov: It's a USA government run website and is generally good for statistical information and primary source material
.edu: It's a higher education website and may lead you to scholarly sources
.org: In general it's a nonprofit
.com: Commercial website
Just because a website is a .com doesn't mean it's bad information, it simply tells you what kind of website it is. As always, use common sense!