Critic cycle in the next step after glycolysis. Pyruvate, the end product of glycolysis, enters the mitochondria matrix. It is decarboxylated oxidatively to produce CO2 and NADH.

It is called a gateway step or link reaction because acetyl CoA acts as a connecting link between glycolysis and Krebs’ cycle or citric acid cycle. It operates in the mitochondrial matrix.
The cycle consists of 10 enzymatic steps, four of which are dehydrogenase and two decarboxylases.
Terminal oxidation consists of 2 processes- electron transport chain (ETC) and oxidative phosphorylation.

Figure: Kreb's Cycle

Kreb's cycle net reaction

Krebs Cycle