Network marketing also known as social selling or multi-level marketing is a legimate business model where you sell a product of value and you earn a compensation.
The model is also designed in a way to help your team benefit from your work as well, so the compensations flow up and down the different levels.
A pyramid scheme, also known as a Ponzi scheme is an illegal business model that lacks a product sale, and only involves buy-ins with large sums of money that flow in one direction upwards.