Please explain.

Heterogeneous equilibrium is that in which the substances involved in the reaction are present in different phases. On the other hand, in homogeneous equilibrium, all the substances are present in the same phase.

The equilibrium in which all substances are present in same phase means means all the chemical compounds in reactant and product in chemical equation are in same phase. Same Phase means all are in solid or liquid or in gaseous state. This is known as homogenous equilibrium.
For example,
2SO2 (g) +  O2  (g)  ⇌  SO3 (g)
The equilibrium in which the reactants and product are different state means all the chemical compounds in reactant and product in chemical equation are in different phase. Different Phase means the physical state of the substance are different. 
For example, 
CO2 (g)  +  H2 (g) ​⇌  CO (g)  + H2O (l)

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