QDK is Microsoft Quantum Development Kit.
Installation steps are here, https://docs.microsoft.com/en-us/quantum/install-guide/
But I had some minor trouble installing it, so this is the note.
 Install .NET package, 2.2.0
First, check if you have DOT NET package installed. Do where dotnet and see if dotnet command is available.
If not, go to this site and install 2.2. It's Important that current QDK requires 2.2.x version.
Check if you have the right version:
> dotnet --list-sdks
2.2.402 [C:\Program Files\dotnet\sdk]
3.0.100 [C:\Program Files\dotnet\sdk]
As shown above, I have 2.2.402 installed.
Now install .NET tools:
> dotnet tool install -g Microsoft.Quantum.IQSharp
> dotnet iqsharp install
 Anaconda + Python + JupyterRun Anaconda and create environment, 'qsharp':
> conda create --name qsharp
> conda activate qsharp
Create workspace directory
> cd /d e:\dev\code\
> mkdir qsharp
> cd qhsharp
And install jupyter and qsharp
> conda install jupyter
> pip install qsharp
> conda install ipykernel
Check if qsharp kernel is installed:
> jupyter kernelspec list
Run jupyter notebook:
> jupyter notebook
This is just to show you installing QDK with right .NET version with Jupyter. Jupyter can be utilize the notebook, but I don't see much benefit of using Jupyter in this case. VS or VS code would be better choice as you still have to write the code in Q#.
There are a lot of docs and examples of Q# -- this is a big plus for learning.
Next time, I'll put some notes on VS, VS code and Q#.