css3 property font-face

Question

Why do we use font-face? Don't browser have it's own font's?
i don't know whether browser's have it's own font's but if it does not, they probably might use font's from Internet.

Answer 1

Fonts depend on the operating system not the browser. Some are shared, some others are unique to the OS.
As for the font face rule, Google, for instance, use their own font called roboto which they created. This font does not come in windows or Mac by default. So they use the font face rule to specify the URL from which the font can be downloaded and therefore used in any browser, any OS. This applies for any custom font one might one to use.