English - Either x As Well x Too x Also

Either is used with a negative verb when you are agreeing with something someone doesn't do or like etc.

A - I don't like cheese.

B - I don't like it either. 

A- I haven't seen Lord of the Rings.

B - I haven't seen it either.

As well / Too are used with an affirmative verb when you are agreeing with something someone does or likes etc.

A - I love ice cream.

B - I love it too." / "I love it as well.

A- I've seen Gladiator.

B - I've seen it too." / " I've seen it as well.

Also comes usually before the main verb or after be and it is more formal than as well and too. It is used in positive sentences.

I went to Munich last year, and I also spent some weeks in Berlin.

Source: www.learnenglish.de