What is the Formula for Constant? What does Constant even Mean?

-Pressure [Pa] x Volume [m³] = Constant -This Equation will only work if the Temperature is the Same AND if the Amount of Gas stays the Same as Well -Constant just means The Same. If the Pressure was Increased, then the Volume would Have to Decrease, cause the Temperature hasn't Changed, nor has any Gas Came In [If it has, then this Formula will NOT work]