Google Searches vs. Wikipedia

Google searches the entire internet. Note the kind of suggestions made in the drop-down box under the Google input box.
Google search for HVAC.
Google search for refrigeration
Searching for HVAC brings up 17,400,000 web pages plus lots of advertising. The information you want is probably out there somewhere, but it takes a while to browse that many pages.
Wikipedia is just one website on the internet. It is designed to give more focused answers than Google. Every suggestion it makes is to another page in Wikipedia
Notice the difference in color in the text on Wikipedia. Each blue word or phrase is a link to another part of Wikipedia. This makes it easy to go from HVAC to air-conditioning.Wikipedia article on refrigeration.