The enthalpy of a system refers to the heat content of the system. In an endothermic reaction, the enthalpy of the system increases because heat is being absorbed from the surroundings. In an exothermic reaction, the enthalpy of the system decreases because heat is being released to the surroundings.
The temperature of the surroundings can also be affected by endothermic and exothermic reactions. In an endothermic reaction, the temperature of the surroundings decreases because heat is being absorbed by the system. In an exothermic reaction, the temperature of the surroundings increases because heat is being released by the system.
In summary, endothermic reactions absorb heat and have a positive enthalpy change, while exothermic reactions release heat and have a negative enthalpy change. The temperature of the system and the surroundings will change in opposite directions in endothermic and exothermic reactions.