Product
Definition
A substance formed by a chemical reaction: what you get at the end.
Technical definition
A product is a chemical species formed during a chemical reaction, written on the right side of a chemical equation. Its identity and amount are predicted by the balanced equation and the reaction stoichiometry.
Example
In 2H2 + O2 -> 2H2O, water is the product.
Common confusion
The product is what the balanced equation predicts under ideal conditions. Real reactions can also make side products or stop early, so actual yield often differs from the theoretical prediction.