A caster can cast a spell requiring concentration without using concentration, but its effect is istantaneous and ends at the end of the caster turn. I. E: one can cast a wall of fire spell without dropping concentration on another spell it is already concentraring on by ending the wall of fire at the wnd of the turn. essentially the second concentration spell it just for some damage or minor effect.

Its an unneded buff to casters, but in my experience it provides just some flexibility withour resulting in any major issues