Google and Facebook both use CPC to collect advertising fees. You only have to pay when users click on your ad.
However, if you run Google Adwords, you will have to pay a much higher fee depending on the level of competition of the keyword. For example, for the keyword "house moving" on Google Adword, you will have to pay 20,000-50,000 VND/click while running ads on Facebook only has to pay 100-2000 VND/click.
The explanation for this big difference is the quality of the click. As mentioned above, Google directly targets people with real needs when searching on Google, while Facebook only relies on interests and demographics similar to the target audience you set.
