On a very basic level, running ads on Google means that when someone searches for something on the internet, an Ad you create appears. It's noted with the word 'Ad' in front of it and is typically at the top of the page. Ads appear when the keywords we choose match a person's search online. So, if you're a Chiropractor, we add that word (and dozens of others) to a list of words or phrases people might type into Google when looking for a healthcare practice like yours.
There are many ways to advertise using Google's Ad platform and the search method mentioned above is just one of them. Google also has partnerships with many websites that also show their ads. So, after someone does an online search, these ads will begin to appear on other websites that person/computer visits. A third way that ads are delivered to people is by matching the Advertiser's keywords with a news article or blog post's keywords. So, a person could be reading an article about back pain, for example, and Google would be showing ads for local Chiropractors on that page even though the reader might not have conducted a search yet for one.
In addition to creating keywords, I also recommend adding negative keywords. For example, if you're a Psychotherapist, we would add the keyword 'therapist' to your ad campaign. Meanwhile we would also add the word 'massage' as a negative keyword so that anytime a search term includes massage (i.e. massage therapist), the ads would not appear.