Hello Christinalty25
In Switzerland, nobody books a train. Our train tickets are for a route, not a train, with the only exception of Supersaver tickets. Thus, with a point-to-point ticket you can take any train serving along your route.
Having a Saver Day Pass, you can use the public transit even more extensively, at will, for one day; only certain PE trains need a reservation. In other words, a Saver Day Pass is an “all-you-can-eat” train ticket, as our colleague @Krist uses to say to explain the great flexibility of a Saver Day Pass.
More information on seat reservations here:
https://community.sbb-tickets.cc/blog/23887-demystifying-seat-reservations-on-swiss-trains-a-comprehensive-guide
Kind regards,
Roland