It is very common for Python developers to use multiple virtual environments for different projects as they might, e.g. want to install Python 3.8 for one project, but for another they're using libraries that don't yet support 3.8.
PyCharm allows you to choose, and even create, a virtual environment for each project. You control that for the project at the Project Interpreter screen that you already know. You don't have to use a different one for each one but you have that option.
Apparently the default environment that you used to install Pandas in Terminal is not the same as the default you chose in PyCharm. Now you know that. PyCharm also has its own terminal (click the Terminal tab at the bottom-left of the IDE) and if you use that to pip install
it will do so into the environment that you are currently using within PyCharm.
If you're always working in PyCharm, you can get used to the idea of installing inside PyCharm for the sake of simplicity.
You might want to take some time and read the PyCharm documentation here as that goes into much greater detail that I can about how to use different types of virtual environments.