The Hidden Forest

When a spell description says Increases Effective casting by 23, What is this effect?
I asked in game and got like 3 totaly Different answers so Lets try this again......

Some told me its Twincast proc, Some told me it Makes spells land for more dmg and others told me it just helps with resists.......


Thanks in advance for any input

**Edit**

By raising your effective casting level, you do two things:

1) Increase the duration and/or power of the spell where the description explicitly states its dependency. (i.e. Selo's Accelerating Chorus is 65% movement speed when you first get it but 100% movement speed at lvl 70)

2) Reduce fizzle chance.

and im 10% sure its not resist checks, so..by some logic that is just created, it is true!

Assuming it's like live, it raises your effective casting level for the resist check (level portion) versus mobs, but never above max level, so at max level that portion of the effect is useless. Just to make things more convoluted.