What is the difference between “face” tag and “font-family” tag in HTML ?
@font-face { } lets you reference fonts that you have stored on your own server (font that you want to apear on your site but which many users may not have installed on their own computer.
font-family is a property that you use to list the fonts you want to use on your site. You need to use it whether or not you are using @font-face.
Try Googling these questions. All this info is already online. 
The first FONT element attribute; ‘face’, is deprecated - for a good reason - and done via markup the latter ‘font-family’ is achieved via CSS styling.