1 - Products
Reactants are located on the left side of the equation, therefore, products are located to the right.
2 - Diatomic
Diatomic are those molecules formed by 2 atoms of the same kind.
3 - Coefficients
Coefficients are the little numbers added beside the atomic abreviations which represent how many of those atoms are in the equation.
Hope it helped,
BioTeacher101