Translation:They are two totally different attitudes.
son = they are (well, it means "are" for the third person plural, so the "they" is always implied if there is no explicit subject give)
But as bf2010, hay = there is/there are
"The two attitudes are totally different." would be "Los dos actitudes son totalmente diferentes."
They: pronoun [third person plural] 1. used to refer to two or more people or things previously mentioned or easily identified.
Oxford dictionaries: http://oxforddictionaries.com/us/definition/american_english/they
"They" is used to refer to two or more people or things, in this sentence the subject is not explicit but is asummed that exist.. "Attitudes" are not humans but can be considered as things so "they" goes in the sentence When the subject is not said in the sentence, in spanish we calle it "sujeto tácito"