"You go to bed."
Translation:Você vai para a cama.
It depends on the situation. "Ir a" is used with countries, cities, towns and other physical locations ("Ir ao banco" - go to the bank; "Ir ao supermercado" - go to the supermarket), and that also includes metonymic locations - cases where the job of the person you're seeing ends up acting as a reference to the place they work in; e.g. Ir ao médico - "go to the doctor"; Ir ao barbeiro - "go to the barber". The idea it carries is that you'll go there, but you'll eventually go somewhere else.
"Ir para" has a stronger sense of finality, usually with the sense of going somewhere and staying there for a while. It can also be used for physical locations when you're staying and not just visiting (Ir ao Brasil nas férias vs. Ir para o Brasil trabalhar). It's this idea that distinguishes "Ir a casa", which implies you'll go there for a bit or to perform some errand, but that you'll leave later; from "Ir para casa", which implies that you don't have plans later. The same train of thought that be extended extended to other words like "quarto":
- Perdi o meu celular! Vou ao meu quarto ver se o encontro. I lost my phone! I'll go to my room to see if I left it there.
- Depois do jantar, fui para o meu quarto e acabei os deveres da escola. After dinner, he went to my room and I finished my homework.
Technically, this could also be extended to "cama", but there aren't many instances where you'd need to "go to your bed" just for a while (probably would only come up when you need to pick up something you left there); in any case, "Ir para a cama" means "To go to bed" (with the intention of sleeping - or not - but what matters is that you'll stay there for a while).