A standard poodle is any poodle over 15 inches in height. A moyen poodle is usually between 16-20 inches. A moyen is not a recognized size in AKC at this time because it would fall under a "Standard" sized poodle usually. Moyen poodles are usually wanted because they are a bit smaller than the regularly seen standard and some people want a smaller sized pet over a larger. The size doesn't affect the intelligance or build of the poodle in any way. Moyen poodle puppies usually look the same in their early weeks like standards, but as they grow you can see the size difference. The weight of a moyen can range from 20-35 pounds.
A standard poodle puppy will usually take up to 24 months (2 years) to mature and finish growing.