What is theoretical yield?
theoretical yield = moles of limiting reagent / molecular weight of the product
Simplified it means how much product can be produced under ideal conditions with the given amounts of the reactands.
This is not true, experimental yield is can be higher than theoretical or equal theoretical yield. If the experimental yield is greater though, that means that something went wrong in the experiment and that was most likely a contaminant. Ideally, you want to be as close to the theoretical yield as possible.