Resume e-learning

When I have started the Storyline 360 e-elearning via the web link and then go into it later, I will be asked if I want to start where I last finished. I am thinking about how it recognizes that I have worked with e-elearning before? Is it via IP address or is it some other recognition parameter? Why I wonder is how it works if I attend the training via the web link and there are several people who attend the training on the same computer?