Concentration is a component that is not necessarily crucial in every spell. Saying the incantation and performing the wand movement for the Wand-Lighting Charm, for instance, will cause the tip of your wand to illuminate without the need to concentrate heavily on a target.Without the proper concentration, you might find yourself levitating the table instead of the chair you had intended to levitate. You may find that, instead of directing the trunk you had intended to charm with the Locomotion Charm, you are moving your bed around and it has unfortunately crashed into the trunk you had meant to move.

Spell modifiers 

a modifier is a word or short phrase added to the end of a spell to modify the target or effect.

The sunlight charm

Incantation: Lumos Solem (‘LOO-mos so-LEM’)

Wand Movement: Single counter-clockwise loop ending with the wand pointed toward the target.

Willpower: Low to very high; determines color and intensity of light.

Concentration: High; the target of the light.

The dancing lights charm

Incantation: Lumos Numerosa (‘LOO-mos Noom-air-O-sa’)

Wand Movement: Single counter-clockwise loop, then several rapid counter-clockwise loops.

Willpower: None

Concentration: High; concentration should be maintained on all the orbs, and determines how many can be created.