I am seeing in several places in the Esri documentation things like:
The following Python window script demonstrates how to use the SelectLayerByAttribute function in immediate mode.
ArcGIS Help 10.1 - > Select Layer By Attribute (Data Management)
What is immediate mode and what other modes are there?
If you have a python editor open and run a command like
>>> import arcpy
That is immediate model. That differs from loading a script, and running a script that has that same line in it
I have 3 incarnations open. ArcGIS Pro's builtin python interface, Spyder's IPython command line window and a standalone script.
Depending on what I am doing I can use several of these to process work. Working with an external IDE like Spyder allows you to connect with ArcMap or Pro easily while doing pure python related stuff at the same time. here is an image