Moissanite - is it a Fake Diamond?

Absolutely NOT!
Let's get things straight, Moissanite is a real stone. It is a REAL STONE that, well you know, happens to look very much like a diamond. 
The story of the Moissanite begun when Mr. Henri Moissan discovered tiny brilliant crystals that looked like diamonds, on a meteor site in Arizona. The year was 1893, and Henri Moissan, as the name indicates, was a French chemist who was investigating the meteor impact of that site. He took the crystals with him and for years believed they were diamonds. It was 11 years before he understood that these were clearly not diamonds but something entirely different.
The stones were named after him. 
Moissanite was found on many occasions but in small quantities, these are clearly far more rare than diamonds and other gems. Interestingly, they've also been found on the outer crust of rough diamonds, and almost always at the sites of meteorite impacts. 
Natural Moissanite is incredibly rare, so what is available today is lab-created. After many years of trial and error, the particles Moissan discovered were successfully synthesized to produce what is now one of the world's most scintillating gemstones.
Moissanite looks very similar to diamond, band is an amazing stone in its own right.
It is a hard stone, on the Moh scale it is rated 9.5. The diamond is 10. While the ruby and sapphire they are 9; which means the Moissanite can scratch these two but they cannot scratch Moissanite.
Visibly, Moissanite looks very similar to a diamond. The only time one can suspect a stone not to be diamond is when it is fairly large and out of one's price range.
For example, you decide to purchase a 6 carat Moissanite (because you can afford to pay that $4500 it will cost), a diamond at that price would be a little less than a carat in size. However, a 6 carat diamond would cost you close to 100K! A harder sell, people around would either assume you hit the jackpot or clearly understand that your stone isn't a diamond but some kind of simulant.
Therefore choosing a more modest size stone would not giveaway that your ring isn't a diamond. Some people are happy to reveal that they have a moissanite, after all it is a stone equally brilliant and stunning in color and clarity, and cut. And as mentioned earlier, nearly as hard!

Have you ever looked at a diamond slowly moving under the light? You'll notice white light and colorful sparks reflected back at you. These being the effect of white light being broken into all the colors of the color spectrum of light. The process of breaking light down into separate colors the way a prism would, is known as ‘dispersion.’ Jewelers and gemologists will describe a stone with more colorful sparkles as "Fiery".

Moissanite is naturally a more fiery stone than diamond.

Which means more colorful sparkles are produced by Moissanite than a diamond would produce!

Reasons people choose Moissanite today:

1) Their fiery nature
2) Their hardness and quality
3) Their price