"Also" is more formal than "as well" and "too", and it usually comes before the main verb or after "be": He speaks Italian, and he also plays chess very well. "Too" is used at the end of a sentence: I'm going home now. - I'll come too. In Britain "as well" is used like "too", but in American English it sounds formal or old-fashioned.

Without splitting hairs, we can use them interchangeably as Jura has described. One thing about English is that repetition sounds like stuttering or "baby-talk", so we would swap them around to avoid this effect. "I'd like to have two." "I'd like to have two, as well" or "I'd also like to have two". ("I'd like to have two, too" sounds silly.)

Often they can be used interchangeably: Examples: - I saw that movie. - I did too/ I did as well / I also or so did I. Sometimes the placement varies: - John also saw the movie. - John saw the movie as well. - John saw the movie, too.