It means it's a syntactic unit. In Grammar is a group or set of words that can be synthesized or abbreviated into a single, or that can have the function of a single, within a sentence. Depending on the context, you can take the function of name (noun), verb, adverb , adjective and even preposition . For example the prayer "The sky blue sky lacked clouds". Heaven, is a nominal phrase and can replace in prayer "the sky blue sky" and that in this case, is the subject of prayer.
From the Greek syn-: with, together with taxis taxeos: placement, management, disposal and the suffix - ma: result of the action: Group of words in order. It is the unit of syntactic function which has a nucleus and other elements ( determinants, prepositions... ). The phrase is known by the kernel or by function. Thus speaks of Syntagma-nominal or sintagma-sujeto. There are nominal, verbal, adjectival, adverbial and prepositional phrases. Syntagma Square is today the heart of Athens after the referendum in which we are all Europeans that we want another Europe.
