MLM is Multi Level Marketing also known as Network Marketing is a means of selling products essentially by referrals from one person to another. It has been officially around for something over 65 years. Being much related to word of mouth advertising, it's been around since day one.
Some people love it and become almost evangelized into their company or "system". Some hate it with the same vengence. If done honestly and in an up front manner, it can be a good marketing system for company, distributor, and buyer.
I market a liquid vitamin product via referral marketing as linked below. I lead with the product and only discuss the business when a buyer is interested in that area.