Aiming a Spell
You must make choices about whom a spell is to affect or where an effect is to originate, depending on a spell's type. The next entry in a spell description defines the spell's target (or targets), its effect, or its area, as appropriate....
Target or Targets: Some spells have a target or targets. You cast these spells on creatures or objects, as defined by the spell itself. You must be able to see or touch the target, and you must specifically choose that target. You do not have to select your target until you finish casting the spell....
Effect: Some spells create or summon things rather than affecting things that are already present.
You must designate the location where these things are to appear, either by seeing it or defining it. Range determines how far away an effect can appear, but if the effect is mobile, after it appears it can move regardless of the spell's range....
Area: Some spells affect an area. Sometimes a spell description specifies a specially defined area, but usually an area falls into one of the categories defined below.
Regardless of the shape of the area, you select the point where the spell originates, but otherwise you don't control which creatures or objects the spell affects....
Burst, Emanation, or Spread: Most spells that affect an area function as a burst, an emanation, or a spread. In each case, you select the spell's point of origin and measure its effect from that point.
A burst spell affects whatever it catches in its area, including creatures that you can't see. It can't affect creatures with total cover from its point of origin (in other words, its effects don't extend around corners). The default shape for a burst effect is a sphere, but some burst spells are specifically described as cone-shaped. A burst's area defines how far from the point of origin the spell's effect extends.
An emanation spell functions like a burst spell, except that the effect continues to radiate from the point of origin for the duration of the spell. Most emanations are cones or spheres.
A spread spell extends out like a burst but can turn corners. You select the point of origin, and the spell spreads out a given distance in all directions. Figure the area the spell effect fills by taking into account any turns the spell effect takes.