Calcium channel blockers (CCBs) are medications that lower blood pressure by preventing calcium from entering heart and arterial cells, leading to vessel relaxation and reduced heart contraction strength. Examples include amlodipine, diltiazem, and nifedipine, which are used to treat conditions like hypertension, angina, and arrhythmias. CCBs are available in short-acting and long-acting forms, affecting their duration of action.