If you consider a pressure & temperature (P-T) equilibrium curve for a single pure component, the vapor and liquid are at equilibrium with each other along the equilibrium curve. As you increase the pressure and temperature along the equilibrium cure it reaches a point known as critical point (generally denoted as 'C' on equilibrium curve). Pressure and temperature at this point is known as critical pressure (Pc) and critical temperature (Tc). For a pure component liquid cannot exist as a separate phase above critical point. Above critical point the system is referred as dense fluid and not vapor or liquid.
In a multi component mixture critical point separates bubble point and dew point curves.