Exothermic and endothermic reactions are really interesting because they deal with energy in different ways.

Exothermic Reactions: These types of reactions let out energy into the environment. Usually, this energy comes out as heat.

Imagine burning wood in a campfire. When you do that, the fire gives off heat. Another example is when our bodies use food to produce energy. In these reactions, energy is released, which we can show as a negative change in energy (called enthalpy, or $\Delta H$).

Endothermic Reactions: On the other hand, these reactions take in energy from the environment. This makes the surroundings feel cooler.

A great example is photosynthesis, which is how plants make their food using sunlight. In this case, energy is absorbed, and we represent it as a positive change in energy ($\Delta H > 0$).

So, the key difference is how energy moves: exothermic reactions release energy, while endothermic reactions absorb it!