The crystals are trichomes, as they start to turn amber that's when you know to harvest depending on your desired effect. They contain the majority of THC in the plant. You'll see long white "hairs". They are called pistils, they collect pollen in order to make seeds. They start white and naturally turn color/die over time. Some growers harvest based on their pistils but you have to really know your strain to do that. If you have a simple scope, trichs are the way to go imo.
How early your trichomes come in may mean shes a faster maturing plant or that you've been doing a good job growing them. Its definitly a good sign I promise.