Chapter 2 Clarification needed on "Create a Test Set'

@ageron The Book @page 55 states" Well, this works, but it is not perfect: if you run the program again, it will generate a different test set! Over time, you (or your Machine Learning algorithms) will get to see the whole dataset, which is what you want to avoid."

Question: Does Machine Learning algorithm retain learning from previous execution?
Followup questions:
If Yes , where do they retain how can we access/erase them?
If No, then how will machine learning algorithms see the whole dataset Over time ?
Please elaborate.

Thank you.