Hello Danaslp
On trains within Switzerland, seat reservations are not obligatory and are therefore not included in the train ticket.
Seats may be reserved in trains which are marked “R” (reservation possible), “RE” (reservation recommended) or “RR” (reservation mandatory) under “comments” in the online timetable.
Detailed information on the various booking options are available under: https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/seat-reservations.html
I wish you a nice day.
GiorgiaB