the diiference between too and either
Both words have several meanings and forms, but as an adverb they do overlap.
The difference is that "too" is follows a positive constructions and "either" follows a negative constructions.
I want to go there, too
I don't want to go there, either
You may use too for either sentence if you use it before the construction:
I, too, want to go there.
I, too, do not want to go there.