What is Aromatic and Möbius transition states?

An aromatic transition state is a cyclic array of orbitals in a pericyclic transition state that, like a Hückel ring, is stabilised when it holds $4q + 2$ electrons. A Möbius transition state has an odd number of sign changes between neighbouring orbitals around the ring (one antarafacial twist); it is stabilised with $4q$ electrons.