The only differences are the origin and the price.

In short; there is nothing 'fake' about a lab-grown diamond.
Lab-grown diamonds are 100% atomically identical to mined diamonds.

Other than the origin, there is no difference between a mined and a lab-grown diamond. They are identical in chemical, optical, and physical composition down to the atom.
Lab-grown diamond is grown in highly controlled laboratory conditions.
A growing chamber simulates the exact conditions a mined diamond would have undergone millions of years ago deep within the earth’s surface.

Mined diamonds are a 100% carbon crystal structure, that is 10/10 on the Mohs hardness scale, with a refractive index of 2.42.

Lab-grown diamonds are a 100% carbon crystal structure, that is 10/10 on the Mohs hardness scale, with a refractive index of 2.42.

On average customers are purchasing a lab-grown diamond that is 40% larger, and of higher quality than a comparable natural diamond while staying within their budget.