difference between too and also and as well

Difference between "too", "also", "as well" and 

• The adverbs also, as well and too have similar meanings, but they do not go in the same position in sentences. Also is usually used with the verb. Too and as well usually go at the end of a sentence or clause. Note that ‘as well’ is not very common in American English.

  He not only plays; he also works.
  He was fat, and he was also short.
  He not only plays; he works as well.
  He was fat, he was short as well.
  He not only plays; he works too.
  He was fat, he was short too.

• The difference is their "POSITION" in the sentence.
  
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  ~> "AS WELL" and "TOO" go to the end of a sentence (a clause) 
  
  For example:
  We can sometimes leave out the subject as well.
  We can sometimes leave out the subject too.
  
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  ~> The word "Also" is more likely to go before the verb:
  For example: We can also sometimes leave out the subject.
  
  
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          ~> Please remember: 

          "Also" is more formal than as well and too.

           "Too" is much more common in spoken and informal English. It is used at the end of the sentence, but                 cannot be used in negative sentences!!

          "As well" is used like too, at least in British English, but in American English as well sounds formal or old-            fashioned.

• As the above answerer hinted, "too", "also", and "as well" all convey the same meaning. Whatever subtle differences among them there must have been at one time have now certainly been lost, and it's only a matter of choosing which one sounds more natural in the given sentence. "Also", and to an even greater extent, "as well", do sound more formal than "too", so there is that to consider.
  
  "So do I" works in this case, as long as the word that the pro-verb "do" refers to is immediately obvious from the context.

• Too - Also - As well - So do I
  
  Here I found very interesting article about the topic:
  
  What’s the Difference Between “Too” and “Also”?
  by Maeve Maddox
  
  In conversation both words, too and also, are used interchangeably with the sense of “in addition”:
  
  Our friends went too.
  Our friends went also.
  
  In such a sentence the too at the end is felt to be more natural than the also. The word also is more likely to go before the verb:
  
  Our friends also went.
  
  The use of too in the sense of “in addition” is not confined to the end of a sentence:
  
  I, too, believe that children are more intelligent than they are given credit for.
  
  They, too, wanted to see the movie.
  
  The word too can be used to modify adjectives:
  This coffee is too hot to drink. Here the sense of too is “to a higher degree than is desirable.”
  
  The word also can have the meaning “in the same manner as something else.”
  
  Few young people read Scott anymore. George Eliot is also neglected in today’s school curriculum.
  
  In conversation it doesn’t matter whether you use too or also, or where either falls in the sentence.
  
  In writing it’s a good idea to give some thought to how the words are being used, and to how often you use them.