In which reaction will heat be released–exothermic reaction or endothermic reaction?

Heat is released in exothermic reactions.

Exothermic reactions are those reactions in which heat is released.
For eg. $\mathrm{C}+{\mathrm{O}}_2\to {\mathrm{CO}}_2+\mathrm{Heat}$

Endothermic reactions are those reactions in which heat is absorbed.
For eg.
$$\begin{gathered} \mathrm{C}+2\mathrm{S}+\mathrm{Heat}\to {\mathrm{CS}}_2 \\ \mathrm{C}+2\mathrm{S}\to {\mathrm{CS}}_2-\mathrm{Heat} \end{gathered}$$