A spell's Duration line tells the character how long the magical energy of the spell lasts.
Timed Durations: Many durations are measured in rounds, turns, minutes, hours, or some other increment. When the time is up, the magic goes away and the spell ends. If a spell's duration is variable the DM rolls it secretly.
Instantaneous: The spell energy comes and goes the instant the spell is cast, though the consequences of the spell might be long-lasting.
Permanent: The energy remains as long as the effect does. This means the spell is vulnerable to dispel magic.
Concentration: The spell lasts as long as the character concentrates on it. Concentrating to maintain a spell is a standard action that doesn't provoke attacks of opportunity.
Anything that could break the character's concentration when casting a spell can also break the character's concentration while the character is maintaining one, causing the spell to end (see Concentration, below). The character can't cast a spell while concentrating on another one. Sometimes a spell lasts for a short time after the character ceases concentrating. In these cases, the spell keeps going for the stated length of time after the character stops concentrating. Otherwise, the character must concentrate to maintain the spell, but the character can't maintain it for more than a stated duration in any event.
Subjects, Effects, and Areas: If the spell affects creatures directly, the result travels with the subjects for the spell's duration. If the spell creates an effect, the effect lasts for the duration. The effect might move or remain still. Such effects can be destroyed prior to when their durations end. If the spell affects an area, then the spell stays with that area for the spell's duration. Creatures become subject to the spell when they enter the area and become no longer subject to it when they leave.
Touch Spells and Holding the Charge: If the character doesn't discharge a touch spell on the round the character casts the spell, the character can hold the discharge of the spell (hold the charge) indefinitely.
The character can make touch attacks round after round. The character can touch one friend (or the character can touch his or her self) as a standard action or up to six friends as a full-round action. If the character touches anything with the character's hand while holding a charge, the spell discharges. If the character casts another spell, the touch spell dissipates.
Discharge: A few spells last for a set duration or until triggered or discharged.
(D): If the Duration line ends with "(D)," the character can dismiss the spell at will. The character must be within range of the spell's effect and must speak words of dismissal, which are usually a modified form of the spell's verbal component. If the spell has no verbal component, the character dismisses the spell with a gesture. Dismissing a spell is a standard action that does not provoke attacks of opportunity. A spell that depends on concentration is dismissible by its very nature, and dismissing it does not require an action (since all the character has to do to end the spell is to stop concentrating).