These diagrams show how much potential energy molecules have at different stages during reactions. Itโs like mapping out how much effort you'll need at different points when pushing that boulder up and over the hill.
Transition State/Activated Complex: This refers to an unstable arrangement of atoms that exists momentarily at peak point in activation-energy diagram before transforming into products. Itโs like the boulder teetering at the top of the hill before it starts to roll down.