dev = qml.device(“default.qubit”, wires=3)
When I set the name of the device as “default.qubit”, it will load a simple state simulator of qubit-based quantum circuit architectures.
Also, we can assign the device we want to simulate on (i.e., ibmq, cirq.simulator, and braket.aws) by changing the parameter of “default.qubit”.
However, I am confused about which quantum computer the “default.qubit” simulates on.
Any help would be greatly appreciated!
Hi @jameshuang900716 , welcome to the Forum!
When you use “default.qubit” on your laptop, then the simulation happens on your laptop. Pretty cool right? 
This is useful when you want to run simulations that might take a long time.
If you use ‘default.qubit’ on Google Colab or qBraid, then the simulation will run on Google’s or qBraid’s servers respectively.
If you’re starting to learn quantum computing I’d recommend starting by going through the PennyLane Codebook. This will help you learn quantum computing theory and programming in parallel, so you’ll get the knowledge and skills all in one 
.
Start with the learning path on Foundations of Quantum Computing, and make your way through other learning paths as you go!