fontWithName:Size:. You supply a name and a size, and the UIFont class hands you back a UIFont instance corresponding to a font with that name and size.
familyNames. It returns an array of strings (that is, an NSArray of NSString instances) consisting of the names of the font families installed on this device. Because this method has to do with fonts, the UIFont class is as good a place as any to put it.
Most methods that you write will be instance methods, but now and then you might write a class method. When you do, your purpose will probably be similar to those examples.