The number value tells the equilibrium ratio of products to reactants. In an equilibrium mixture both reactants and products coexist. The value for K is large when products dominate the mixture. The value for K is small when the reactants dominate the mixture. The expression for an equilibrium reaction is determined by the coefficients in the balanced equation.
Reversible reactions have analogous mechanical examples.
One tank has no fish and the other contains 10 identical fish. Predict what will happen when you open the gate that blocks access to the empty tank. I hope we agree. The fish will swim around and the 10 fish will eventually distribute themselves between the two tanks. If you took pictures of the process as the fish swim around they might look like these.