Google Ads allow you to get paid exposure to users of the Google search engine on a per-click-basis. This is one of the most poplular ways of generating traffic to a website and therefore also more expensive. What makes this advertising form special is that Google ads are serving an active search intent and are therefore highly effective for certain search queries.
Keywords & Search intent
Until now, the key driver for searching and organizing information on the internet, was text or keywords. In order to interact with computers, humans used keywords that both entities could understand. This interaction between the machine and the human is being used by Google to inject advertising messages based on what is being searched for. Very often the search intent of a query is very straight-forward and obvious making it very popular for advertising messages. Other search phrases, are less frequent and less popular by advertisers.
CPC stands for cost-per-click and is the actual mechanism, how Google is earning money with Google Ads. Everytime an ad is clicked, the advertiser has to pay a fee that is being defined real-time in an auction process. As long as an ad is not clicked, the advertising is not paying anything.