Do you need a passport to travel to Switzerland?

Not if you are a citizen of an EU or Schengen Area country which issues national identity cards, then you can enter Switzerland using that identity card. Otherwise you need a passport.

If you are entering Switzerland via the land borders there are not normally any passport / ID card checks, as Switzerland and all countries bordering it are members of the Schengen Area. But you still need to carry your passport or ID card as this is a legal requirement in Switzerland, and you might be unlucky and get asked to show it at the border.