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

Explanation

The chemical reactions which occur with the evolution of heat are called exothermic reactions.
For example, `C_((s))+O_(2(g))toCO_(2(g))+"Heat"`
`2H_(2(g))+O_(2(g))to2H_(2)O_((l))+"Heat"`
The chemical reactions which occur with the absorption of heat are called endothermic reactions.
For example, `N_(2(g))+O_(2(g))+"Heat"to2NO_((g))`
`2NH_(3(g))+"Heat"toN_(2(g))+3H_(2(g))`