Kidou is divided into two types. Hadou (Way of Destruction) and Bakudou (way of binding... or more accurately, way of everything else.)

Each Kidou spell has a rank (which determines it's power and effects) and a type, which determines other facets about the spell. A spell's 'number' therefore, is the Rank in the ten's digit, and the type in the 1's digit. Hadou 35, for example, is a 3rd rank, Solid Projectile Destructive Spell.

Below are the types, within each of which is a large swath of potential customization for each player's own unique Kidou. I'll detail the power ranks later.

Bakudou Types:

0: Zanpakuto Related
1: Constant Seals
2: Defensive Barrier (shields and such)
3: Restrictive Barrier (capturing people, restraining explosions, etc)
4: Constriction (chains, bindings, that sort of thing)
5: Camouflage/Distraction spells
6: Repulsion Barriers
7: Marking Seals (such as for tracking, or homing attacks, etc)
8: Mental/Telepathic spells
9: Trap Spells (Set and forget, typically incorporates a Hadou to blow up the one who triggers the trap, or inflicts a debuffing seal on the victim.)

Hadou Types

0: Zanpakuto Related
1: Meelee augmentation
2: Impact (pure physical force, think Tri-beam)
3: Wave (Incinerates the target, think Kamehameha)
4: Beam (Pierces the target)
5: Solid Projectile (self explanatory)
6: Burst (Area of Effect that emanates from the caster)
7: Melee Extension (Fist of the Beast King, etc)
8: Orb (Throws a sphere of energy, like Shakkako)
9: Trap (unlike trap Bakudo, a trap Hadou is a spell that attacks from all directions, such as Black Coffin, or Hellzone Grenade. The two are often used together, however.)