The only difference is in their placement in the sentence. Too is used at the end of a sentence. Also usually goes before the verb or adjective. For example: He likes chocolate I also like chocolate. ( you can't say "I like chocolate also") I like chocolate, too.

'too' has much more meanings and too=also ONLY at the end of a sentence. 'too' has much more other meanings. Among them: likewise, really, actually, moreother, extremely, highly, either, over etc.