Every time we've learned about WW in school Switzerland was only mentioned with "They were neutral" and then moved on to another country.

I'm wondering why was their neutrality respected? It had borders with Germany, Austria & Italy, making it mostly surrounded by nazi countries, and, if I'm not mistaken, had German residents just like e.g. Czechoslovakia - it only seems strategic they would get invaded.

So what made the difference and decision to not invade them, unlike e.g. the already mentioned Czechoslovakia?

Additionally, were there any plans to invade them at further stage, or not at all, and if so, why not?