Recap: when warm, moist air near the ground is heated by the Sun it may become warm enough to start lifting convectively. The temperature at which this process begins is called convective temperature. If this temperature is not reached, convection will not begin.
Other processes may help the air to rise and convection to begin, even if convective temperature is not reached. These processes are known as forcing. Forcing mechanisms include: fronts (warm front, cold front) and outflow boundaries (small-scale cold fronts produced by individual thunderstorms), surface wind convergences, orographic lift and upper level forcing.
We will go into much more detail of initiation of convection (storm initiation) in one of future tutorials.