Where Facebook ads allow you to target users based on demographics, Google Adwords allows you to target a clientele based on what they're looking for. The huge advantage of this is that the quality of the clicks you receive from Google Adwords campaigns is exceptionally high, as the traffic is generated by users who have already commenced the buying process. There's no need to convince them to buy, they already know what they’re looking for, and are simply trying to decide whom to buy it from. Google Adwords gives you the 1-up on your competition by placing paid-for ad results alongside organic ones, letting the consumer decide which result is ultimately best for them.
Essentially Google Adwords offer you an opportunity to source high-quality leads from a market of willing buyers.
It really that simple.