Question

define reactants and products

Answer 1

The compounds which react in a reaction are called reactants,
→These are present in left hand side

The compounds which are formed after the reaction are called products.
→These are present in right hand side
example:-
H2+O2------→H2O
in this H2 and O2 are reactants where H2O is product

Answer 2

♦ Reactant

• Reactants are substances which takes part undergoes the reaction.
• They are present in left side of the Chemical Equation.

♦ Product 

• Products are he results of the reaction is chemical equation.
• Products are present in right side of chemical equation. 

Example:

NH₃ + HCl → NH₄Cl

Here: 
Reactants => NH₃ and HCl
Product => NH₄Cl