We have been building out and running PPC ads for over 25 years. We started with the original PPC engine - GoTo.com, and have never stopped managing them for our clients.
The major players in the PPC market are: Google Ads, Bing Ads, and LinkedIn Ads (which can be very expensive).
There are the Search Networks and the Content Networks, and they require different strategies to implement and run successfully. And, what works for one industry or business vertical, might not provide online advertising success for another.