A frigate in the terms as I understand it and to quote something I once read is;
The smallest warship capable of undertaking independent operations
A corvette on the other hand is more likely to have a primary focus in one area (i.e. ASW, ASuW or AA) with a limited limited or no capabilities in the other two. Hence in high intensity operations it is dependent upon the support of larger vessels for protection in areas its lacks. Typically they also lack the range and endurance of other large surface combatants I think the German K130, Malaysian A100 are typical examples of corvettes, where the focus is on surface warfare with limited AA and virtually nil ASW.