Structural Grammar describes the grammar of a language based on the analysis of the description of the "structure" of the sentences. TG Grammar, or Transformational Grammar, is a bit more complicated.
By the mid-20th century, Noah Chomsky, who had studied structural linguistics, was seeking a way to analyze the syntax of English in a structural grammar. This effort led him to see grammar as a theory of language structure rather than a description of actual sentences. His idea of grammar is that it is a device for producing the structure, not of langue (that is, not of a particular language), but of competence--the ability to produce and understand sentences in any and all languages. His universalist theories are related to the ideas of those 18th- and early 19th-century grammarians who urged that grammar be considered a part of logic--the key to analyzing thought. Universal grammarians such as the British philosopher John Stuart Mill, writing as late as 1867, believed rules of grammar to be language forms that correspond to universal thought forms.
Hope this helps!
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