Sentence structure is the way a sentence is arranged, grammatically. The sentence structure of your writing includes where the noun and verb fall within an individual sentence.
Sentence structure depends on the language in which you're writing or speaking. It's common in English for a simple sentence to look like this: "She throws the ball." In this case, the sentence structure is "Subject, verb, object." There are many ways to make the sentence structure much more complicated while still providing a framework for the information you're conveying and being grammatically correct.