You use "Also" to agree about something that you have already said in the first sentence. An example would be: "She is very good writer. Tomas also has talent for that. Whenever you use "Too", you are saying that all the people talking agree about something or share the same idea. E.g: Katy is very good at Math. Harry is good at it "too". Another example would be: "I love italian food. I like Chinese food too" Marcos thinks that he should study cience. His mother thinks agree about it too. I hope this help you.

And there's "as well", as well. Or you can say there is "as well", too. "As well" is a touch more informal than "too", but both usually come at the end of the phrase to remind of the addition to the previously mentioned item. "Also" often moves up in the sentence, and serves almost like a conjunction to connect to some earlier idea. It can even come at the front, which "too" and "as well" cannot: "I'd like to have some coffee. Also, I'd like some tea for my friend". Note however that you can put "too" earlier, usually after the subject, to show it's the subject that is being added rather than the object. Compare these two sentences: - "Peter needs a haircut. He needs a new pair of glasses, too." - "Peter needs a haircut. I too need a haircut".

Too and Also can be used interchangeably at the end of a sentence. Example: "I like food. She likes it too." Is the same as "I like food. She likes it also." However, too can also mean more than is needed. For example, "I ate too much, and now my stomach hurts".

Acrescentando ao q o Pablo disse, note que "also" sempre vai no meio das frases, enquanto "too" vai sempre no final. Existem outras maneiras mais adequadas e muito comuns de concordar positiva ou negativamente de algo dito, se quiser saber mais me mande uma mensagem e eu posso te ajudar... Take care