This is a very common question.
The diagram below is a pictorial description of the differences followed by some explanations.
Starting from the bottom:
All the features are configurable and optional.
In case you have not found it yet, there is a white paper with technical details on Cortex-M23 and Cortex-M33 processor.
Great overview Diya - much appreciated! Any chance you have one/can do one on the difference between the M7 and M33?