What is the answer to the following problem?
You in a race. Yoou need to pick up a basketball, go through a door, climb up a rope, and drop the basketball in a waste basket on a shelf at the top of the rope. Which step would you change to make things go a lot faster and how is this similar to speeding up a chemical reaction?
The slowest step in the race is to climb the rope, everything else is easy. So you need to find a way to get up the rope quicker or use something else instead of the rope - perhaps a ladder, a trampoline, or something similar that would get you to the top more quickly. Or you could lower the height of the shelf so you could get to the top of the rope using less energy.
Now how does this relate to a chemical reaction? In many chemical reactions, it is necessary to add some energy to the reaction to get it started. For example, burning paper. Paper is a good fuel but you need to first light a match and put it next to the paper to get the paper started. That small amount of energy results in a large amount of energy being released when the paper continues to burn.
Chemical reaction energy diagrams are sometimes used to illustrate this principle. Imagine you are on a level surface and have to climb to the top of a hill. Once you get to the top you can then slide down the other side. Going up you are doing work (using energy) and coming down you are releasing energy. If you can make the hill smaller in height you can get to the top soon and then get to slide down the other side.