Notes

The structure of a phrase or clause represents the main simple components of those parts respectively. It deals with morphological aspect of specific words/phrases. Put with other words, the structure of a phrase/clause is understood when analyzing its elements within these entities, disregarding the complete structure of the sentence and other parts that surround that phrase/clause.
On the other hand, the function of a phrase or clause represents the role of these entities within a sentence (note that the structure of a phrase/cl. disregards the other elements of a sentence, so it is analyzed within itself). It fulfills the sentence's meaning by operating on it.
A clear distinction and understanding between these two, can be seen as the example below:
Adea wanted to clean her room earlier that day.
Let us analyze closely the first word "Adea". Morphologically, the word category of Adea would be a noun; in syntax a noun phrase (this analysis is disregarding purposefully other elements of the sentence). On the other hand, by function or syntactically, Adea takes the role/function of a subject.