to is a preposition (in / a / per) and the marker of our infinitive verb (....are ...ire ...ere)
e' importante provare = it's important to try.
siamo andati in Svizzera = We went to Switzerland.
sono andato per vederla = I went to see it.
too is an adverb (anche / troppo)
e' piaciuto anche a lei = she liked it, too
era troppo caro = it was too expensive.
Siamo troppe = there are too many of us.