Chemical equilibrium is a dynamic phenomenon happening in a system; meaning that the reaction rates of forward and reverse reaction is equivalent thus the concentration of reactants and products will not change with the apparent change in time. It is being represented with a double arrow when the chemical equation is being written. To further explain the chemistry, let me show you an example.
The reaction `A <=> B+ C` means that
`A -> B+ C` A decomposes to form B and C as
`B +C -> A` B and C reacts to form A
The rate of the formation of B and C is equal to the rate of formation of A. These two reactions happen at the same time. That is why it is called a dynamic equilibrium.