Hello SolMarottoli
You are referring to the Swiss Travel Pass. The SwissPass is a resident product.
The Swiss Travel Pass is your ticket. It allows you to use trains, buses, trams, and boats at will; thus you can hop on and off where and when desired.
Does the Swiss Travel Pass allow free travel on all public transport services? Almost, it does for the regular train lines, buses, as well as in the cities. However, it does not cover most mountain railways and cable cars, or for some of them (e.g. Jungfraujoch), it grants a reduction only. Where the Swiss Travel Pass is valid and how can be seen in the map of validity document on the STP product website:
https://www.sbb.ch/en/tickets-offers/tickets/guests-abroad/swiss-travel-pass-info.html → More on the topic.
Mt. Rigi, Mt. Stanserhorn, Mt. Rochers-de-Naye, Klewenalp, and Stoos are the only mountain excursions which are 100% covered, thus free, by the Swiss Travel Pass.
Do you need reservations for trains? No, except for the Glacier Express (GEX), and Golden Pass Express (GPX). Our trains are, in general, free seating, consequently you can take any available seat in your respective travel class. If you would like to know more about the optional seat reservations, read our blog:
https://community.sbb.ch/blog/23887-demystifying-seat-reservations-on-swiss-trains-a-comprehensive-guide
Please let us know if you have more questions.
Kind regards,
Roland