Difference between Cox Proportional Hazrd Method and Weibull AFT model in lifelines package in Python

Question

I am going through survival analysis using Python's lifelines package.

https://lifelines.readthedocs.io/en/latest/Survival%20Regression.html

While reading ATF; Accelerated Failure time model and Cox Propositional Hazard method, I came to know AFT model is useful when relative failure of 2 population is given, but as I read further, in example AFT is used on single population only. How different it is from just CPHFitter( Cox Proportional Hazard Fitter) ?

I am not able to figure out how exactly acceleration is happening when relative accelerated failure rate is not given in example of AFT - (https://lifelines.readthedocs.io/en/latest/Survival%20Regression.html#the-weibull-aft-model)