Both are diamonds, of course! Both are faceted crystalized carbon, crystal clear, that sparkle in direct light. Lab grown diamonds look and feel just like natural diamonds and they both come is all shapes and sizes.
Fundamentally, the only difference lies in the origin of the diamonds. Natural diamonds are created within the Earth over a billion years, whereas lab grown diamonds are made in a small fraction of that time in laboratories.
They appear to be identical, if you had a lab grown and a natural diamond in front of you, it would be practically impossible to tell the difference because they even have almost identical chemical structures. They have very subtle differences that can only be detected by trained gemologists and sophisticated equipment designed for that purpose.