Question

explain the role of activation energy in a reaction.

Answer 1

The activation energy is the required amount of energy to get your reactants to the transition point, where they will react with each other to form your product or products.

Answer 2

In addition to what @cephalopod3 said,
The activation energy is the amount of energy required to break bonds at the beginning of a reaction,
When a reaction occurs bonds in the substrate must first be broken for new bonds to be formed.

Answer 3

~amount of energy required in order for a reaction to proceed from the reactants to the products.
~ threshold energy that must be overcome to produce a chemical reaction.