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

(N/A) Chemical reactions that release energy in the form of heat,light,or sound are called exothermic reactions.
Example: The reaction of sodium and chlorine to yield table salt:
$Na_{(s)} + \frac{1}{2} Cl_{2(g)} \longrightarrow NaCl_{(s)} + 411 \, kJ$ of energy.
Reactions that absorb energy or require energy in order to proceed are called endothermic reactions.
Example: In the process of photosynthesis,plants use energy from the sun to convert carbon dioxide and water into glucose and oxygen:
$6CO_{2(g)} + 6H_{2}O_{(l)} \xrightarrow{\text{Sunlight}} C_{6}H_{12}O_{6(aq)} + 6O_{2(g)}$