Hello Pablo Sepúlveda
Your understanding is totally correct.
Yes, you simply hop on and off the trains / buses / trams / boats as you like. Some PE trains require a seat reservation, any other public transport service has free-seating. This is why using public transport in Switzerland is so easy; it works like a metro or suburban train in your country.
Let us know if you have more questions. We also do like to hear your experience of using Swiss public transport.
Best wishes,
Roland