As mentioned earlier, the requirement for an atom to be a chirality center is that the atom must be sp hybridized with four different attachments. Because of this, all chirality centers are stereocenters. However, only under some conditions is the reverse true. Recall that a point can be considered a sterocenter with a minimum of three attachment points; stereocenters can be either sp or sp hybridized, as long as the interchanging any two different groups creates a new stereoisomer. This means that although all chirality centers are stereocenters, not every stereocenter is a chirality center. 
Stereocenters are important identifiers for chiral or achiral molecules. As a general rule, if a molecule has no stereocenters, it is considered achiral. If it has at least one stereocenter, the molecule has the potential for chirality. However, there are some exceptions like meso compounds that make molecules with multiple stereocenters considered achiral.