What does one mean by exothermic and endothermic reactions? Give examples.

Exothermic reaction: "Exo" means releases and "thermic" means heat. therefore, an exothermic reaction is a chemical reaction that releases energy through light or heat

It is expressed in a chemical equation:

Reactants → products + heat energy. Example of exothermic reaction: when carbon is burned in presence of oxygen, a lot of heat is released in this process.

Endothermic reaction: An endothermic reaction is a chemical reaction in which energy is absorbed in the form of light or heat.

It is expressed in a chemical equation:

Example of endothermic reaction: when nitrogen is burned in oxygen a lot of heat is required for this reaction to take place.

$N_{2} \ ( g) \ +\ O_{2} \ ( g) \ +\ Heat\ \rightarrow \ 2NO\ ( g)$