A spellâ€™s components are what you must do or possess to cast it. The Components entry in a spell description includes abbreviations that tell you what type of components it has.
Verbal (V): A verbal component is a spoken incantation. To provide a verbal component, you must be able to speak in a strong voice. A silence spell or a gag spoils the incantation (and thus the spell). A spellcaster who has been deafened has a 20% chance to spoil any spell with a verbal component that he or she tries to cast.
Somatic (S): A somatic component is a measured and precise movement of the hand. You must have at least one hand free to provide a somatic component.