Having trouble following along with Pipenv video

Here’s the video I’m talking about:
https://www.codecademy.com/courses/learn-python-3/videos/learn-python3-pipenv

I’m having trouble following along with the video. The screen that’s shows has a text editor along with a terminal.
I was able to install pipenv using CMD terminal fine.

Then he shows using something that has a text editor along with a terminal (12:05 in video). I have PyCharm, and assumed that this would work as well, however the terminal in PyCharm didn’t recognize the first “pipenv --three” command. It said it wasn’t recognized. Also I was in the correct directory.

I was able to get around this by using CMD.exe to type in the commands to install numpy and requests into project 1 and 2 folders.

Then when it says to use pipenv shell, I did this and noticed the title bar of CMD changed to “Select Command Prompt - pipenv shell”
However the next step is to type “python3” and it said the command wasn’t recognized. From 20:24 on out I’m not able to follow along.

I’m confused why different terminals don’t work for certain commands.
For example when it’s required to use Jupyter Notebooks in the Python3 course, I have to go into the Miniconda terminal for it to work successfully. It won’t work in the CMD, or Git Bash terminals.

Why do certain commands only work with certain commands only work in certain terminals?
How can I know which terminal will work for which commands?