We all use Google and see Ads on the right-hand side. We also see Ads on other sites. Where do they come from? How does Google match Ads with the Search/Content? How does the bidding work? How does all this happen in a blink of an eye?. This is a broad overview of Google Ad system, that serves over 30 billion Ad impressions everyday, which is roughly 3.5 lakh impressions every second. All this generates over 45 billion dollars in revenue for Google every year, which translates to roughly Rs 750 crores every day or around Rs. 90,000 every second - all from Ads