A URL is a web address, the string of letters and/or numbers (usually starting with http or https) that lead you to a website. The letters after the final period refer to the website's Top-Level Domain (TLD) and is called a domain suffix (examples are .com or .org). These can tell you what the website is for, or who put it together, and help you decide if a website is reliable enough to use in your research.
What is it? One of the most common domain suffixes, .com signals a Commercial website. This is usually a website for a business or service, and its main objective is sales; many news websites are also .com sites.
Should I use it? .com websites should be used with extreme caution beyond basic information (contact info, mission/vision statements, etc.). Examine news websites very carefully for bias.
What is it? Websites ending in .org are Organization websites, usually for member organizations or nonprofits.
Should I use it? Analyze .org sites carefully. Many are biased toward a specific agenda they're pushing, and sometimes for-profit groups have a .org address. As with .com sites, basic contact information or mission/vision statements should be okay to use.
What is it? .edu signals a page from a College or University website.
Should I use it? Most .edu websites are considered reliable for research, but privately-owned pages from faculty or students might contain inaccurate information. Usually these websites have a ~ symbol somewhere in the web address.
What is it? Websites ending in .gov are pages from U.S. Federal, State, or Local Governments, including agencies; .mil websites contain information from the U.S. Military.
Should I use it? .gov and .mil websites are generally acceptable for academic research papers, but be sure to check what if any vetting process has been imposed on given reports.
You can make Google bring back results from specific domain suffixes by using the command site:.
After typing the word "site" followed by a colon (:), use the suffix with the period (for example, .edu).
EXAMPLE: PTSD site:.gov will return only those results about PTSD that are from .gov websites
You can also use the command to search Google for results from a specific website. In this case, the command would be site: followed by a full or partial web address.
EXAMPLE: PTSD site:www.ptsd.va.gov will return only those results about PTSD that are from the VA's PTSD website