NEM purpose and aspects
The NEM Smart Asset System allows you to totally customize how you use the NEM blockchain. First, your Namespace defines your home on the blockchain where you can name your own Mosaics, provide easy-to-remember names to user addresses, and more.
NEM additional differentiation against competition
Mosaics then are the basic building blocks of Smart Assets that you can use to represent lots of simple things: it could be a coin, a signature, a status update.