Why is the activated complex also known as the transition state?

Answer 1

That is because the activated complex is the maximum energy value between two energy states. The transition state is higher energy than the product so it moves from that state to the product. The energy to move from the reactant to the transition state is the activation energy.
so the process goes reactant to transition state to product.
If the product is higher energy than the reactant the process is exothermic
If the product is lower energy than the reactant the process is endothermic

Answer 2

Transition State Complex

Answer 3

To put it a bit simpler, its called the transition state because it is a temporary joining of the reactants into one large complex after they have collided and stuck together. The bonds rearrange and then the products split off. The transition state may only last for a few microseconds as apart of a reaction taking place, so it really is transitional in nature.

Answer 4

A true 'transition state' is at the peak of the activation energy curve. It sometimes can be isolated in crystal structures as an 'Intermediate'.

Transition states exist in a structure partly resembling the substrate, and partly resembling the product, hence 'transition'.