Do I need a seat reservation for the bus?
Most buses in Switzerland do not require a seat reservation. Some popular pass routes do require them. All other buses can just be boarded with a rail pass (many "rail" passes are actually public transport passes) or a bus ticket, and do not need to be booked in advance. Check the timetable to see whether your bus requires seat reservations.
Essentially you pay for two "services" when you travel by bus:
The ride. You pay for that through a ticket or a rail pass. Some passes do not offer free traveling but discounted traveling. In that case you need both the pass and a discounted ticket to pay for the ride.
The seat. Seat reservations are only required for a few buses.
The ride and the seat are separate components. You can purchase a ticket/pass and a seat reservation together, or you can do so separately. So you don't need a rail pass to purchase a seat reservation. All is fine as long as you posses both when boarding the bus.
If seat reservations are not required for your bus, it may still be possible to book a seat. We recommend only to do so if you're sure you'll be traveling on one specific bus, or if you're traveling in a group.
How to purchase seat reservations?
Depending on the route, seat reservations can be purchased online, through e-mail or by phone. They're also for sale at staffed rail or bus stations.
How to use seat reservations?
You will need to show the seat reservation to the driver before boarding. The seat numbers can be found either over the window or on the seats.