On the given day and until 5am the following day, this pass is valid for unlimited travel via bus, tram, train and some boats.
The day pass is issued in your name, so you cannot transfer it to anyone else. If you lose it, it can be reissued.
Not every municipality sells these saver day passes. Per day, there is a limit to the number issued across the nation. Alliance Swiss Pass shows where they’re available.
The price of the saver day pass depends on the date of purchase and when you want to travel: the earlier you buy it, the more you save. It's available for first- and second-class seats, and for travellers with and without the half-fare card. You can purchase it as early as six months in advance up until the day before your trip.
The day pass portal lets you check availability, prices, and where and how to buy a Municipal Saver Day Pass.
The SBB website provides details on where the GA travel card is valid; this also applies to the saver day pass.