Web fonts allows the design to include fonts that are not already installed on the user's computer.
This text uses a font from google called Indie Flower.
This text uses a font from google called Trirong.
Fonts can be added to the website in two ways:
They can be are added to the HTML by using a link tag or they can be referenced directly in the css by using @font-face. Either way when using them in CSS you reference them in the font-family property.
Fonts can be purchased through sites like this one.
Fonts are also available to the public using an API from Google.
For more information visit:
w3Schools: WebFonts or CSS-Tricks:@font-face