A chemical reaction always tries to go to completion, one way or the other If there is a way for the reaction to go the reverse direction, what is this process called?

A chemical reaction tends to reach a condition of $\text{equilibrium}$; it $\text{equilibrates}$ such that the $\text{forward rate}$ is equal to the $\text{reverse rate}$.
And equilibrium is specified when the forward rate of reaction is equal to the reverse rate of reaction, the quotient of these rates is formalized by the thermodynamic equilibrium constant, ${K}_{\text{eq}}$, where........
${K}_{\text{eq"="[Concentration of products]"/"[Concentration of reactants]}}$