Exothermic and Endothermic
A very short one for you now, we will only look at heat energy accompanying reactions.
An exothermic reaction is one that gives out or produces heat, an example of this is combustion of hydrogen (which is explosive in normal conditions).
Exothermic reactions take place because the reactants have more energy than the products, so extra energy is expelled by heat. Exothermic reactions are also related to the creation of bonds
An endothermic reaction is opposite to an exothermic, it takes in heat.
Endothermic reactions take place because the products have more energy than the reactants, so extra heat energy is taken from the environment. In an endothermic reaction, bonds are broken.