Facebook ads let you directly advertise on the entire Facebook network, focusing on social media channels. Google Ads, on the other hand, are for advertising through the Google Search and Display networks, showing ads on search engines and websites that are part of these networks.
The important difference here is that Google Ads is demand generated, which means the user is actively searching for something. Social media is a whole different affair, so on Facebook there’s no intent, so you’re hoping to get your ad in front of the right person at the right time.