Spell casting may take one of various forms depending upon the caster,
and a spell's effect can be just about anything. Spell casting
generally costs spell points (SPs).

Spell casting is affected by bulk (HELP BULK).

An example:
Help for spell: fireball

Type: Area attack spell
Damage Types:
     Fire: 100%
Maximum Damage: 250
Additional Effects: No
Casting time:   5 rounds          Spell cost: 63 
Spell level: 10                   Spell category: fire
Affecting stats: Int              Resisting stats: None            
Offensive: Yes                    Location: Anywhere
Target: notarget                  Range: room
Components: VS
Alignment: 

 -=Spell Description=-
The Fireball is one of the standard spells for Soselian mages, both
effective
and flashy.  Especially talented mages have been known to juggle fireballs
in
a show before throwing them at their foes.
This spell works on a military unit.

Let's break down this description.

Type:  There are single attack spells, healing spells, area attack
spells, protection spells, and miscellaneous spells.  Single attack
spells affect one target only, healing spells heal the target, area
attack spells harm all targets that are NOT party members, 
protection spells reduce incoming damage while they hold, and
miscellaneous spells don't normally directly impact health. This
fireball is an area attack.

Damage Type:  This is the type of damage the spell does.  There
are fourteen damage types (HELP DAMAGE TYPES). This fireball is,
unsurprisingly, all fire.

Maximum Damage:  This is the most damage a spell can inflict. In
this case, up to 250 damage to every non-party member nearby.

Additional Effects:  This is only listed for offensive spells. When
yes, there's something that will happen beyond the initial damage
of the spell. Effects vary tremendously. Since this says no, the
fireball's magic won't do anything like leave targets on fire nor
knock foes down when it connects.

Casting Time:  This is the number of rounds it takes to cast
the spell.  It can be cast faster with skills like quick chant
or speedsong (HELP SKILL QUICK CHANT, HELP SKILL SPEEDSONG), and
there are skills that show how much longer a spell will take to
cast, like the essence eye skill (HELP SKILL ESSENCE EYE).

Spell Cost:  This is the cost in SPs that the spell requires
to cast.

Spell Level:  This determines how expensive the spell is to study,
as well as the lowest level the spell can be available in a guild.
Higher level spells are generally more powerful.

Spell Category: The kind of magic (HELP SCHOOLS OF MAGIC), which
is unsurprisingly fire in this case.

Affecting Stats:  This determines what statistics help the
caster to succeed in casting a spell or enhancing its effects. In
this case, intelligence will help.

Resisting Stats:  This determines what statistics help the
target to avoid the effects of the spell. It seems nothing can
help against an incoming magical ball of fire save caster error.

Offensive:  Whether this is harmful magic.  Most people on the
street treat casting offensive magic like brandishing a knife.
A fireball is probably more dangerous than a knife.

Location:  Some spells can only be cast indoors, outdoors or,
rarely, in more exotically limited locations. A fireball can
be cast anywhere.

Target:  Some spells require a target of some kind, and some
aren't cast at anything in particular.
notarget - doesn't target anything in particular
obtarget - some kind of object
livingtarget - a player or NPC
playertarget - a player
caster - self-targeting
ranged - the target has to be hit with a projectile
needtarget - can vary
Fireball, in this example, is cast with "cast fireball". Compare
spells which are cast at targets. eg. "cast jolt at monster".

Range: For targeted spells, how far away the target can be. This
includes:
distant - anywhere in the Retroverse
room - in the same room, can be 'look'ed at
ground - on the ground in the room
close - within limb's reach
Fireballs are cast into the room.

Components:  Verbal components require the caster be able to
speak.  Somatic spells require the caster be able to move.  Any
somatic spell requires two hands (limbs) to be free of weapons
or equipment.  For every hand that is filled with an item or
weapon, the caster is penalized one round.  Material
components require something to be in the caster's inventory,
or, rarely, on the floor, to be cast.  Sometimes that material
component is used up by the casting, and sometimes it isn't.  It
depends on the spell.  Spells that are both nonverbal
and nonsomatic cannot be interrupted by jars or actions
that would otherwise interrupt a spell (getting items,
putting items into something else, etc).

Alignment:  This generally determines the alignment necessary
to cast the spell. If the target must be of a certain alignment,
it should be mentioned in the spell description.