It means nearly the same.

"Decoupling" implies, that there's some "coupling" in a conventionel circuit. Yes, this coupling is provided by having all the individual supply pins connected to the same supply voltage. If now a spiky current is drawn by a chip which lets a flip-flop toggle or something else, then this spiky current will flow along the whole supply voltage routing. And if there will be a voltage drop due to unavoidable inductance of supply voltage routing, then all the other chips would suffer from that, unless decoupling capacitors are used with each chip: Then, the spiky current will be drawn directly from according decoupling capacitor and will no longer flow along the common supply voltage routing. The decoupling capacitor works as a bypass, because it delivers the spiky current which need no longer to flow along the common supply voltage routing.
On the other hand, if there is some noise on the common supply voltage, then the decoupling capacitor at each chip will shunt the noise directly to ground. Here again the decoupling capacitor works as a bypass, because it shunts the noise to ground before it can reach the chip.

"Decoupling capacitor" mainly means the situation where noise must be suppressed:
1. directly at the source by delivering the needed spiky currents showing very fast change rates and
2. by suppressing noise developing on supply voltage routing by shunting it directly to ground.

"Bypass capacitor" mostly means the situation, where a circuit draws an enormous current for a short period, which the supply voltage cannot deliver without suffering from a momentary voltage break down.

As you can see, a decoupling capacitor is always a bypass capacitor and vice versa.

Important for working properly is, that decoupling capacitors are used with each chip, and that these capacitors are directly connected to the associated supply pins. According copper traces which do that must be as short and wide as possible. It's best to use a solid geound plane for these connections. This will guarantee shortest and widest connections and the forming of smallest current loops for the spiky currents.

Kai