Syntax has nothing to do with sins or taxes. What a cryin' shame, right?
When it comes to syntax, it's all about sentence structure—how words and phrases relate to each other.
Some texts have syntax similar to that of everyday spoken English (like the sentences you're reading right now). Other stuff has crazier syntax, which makes it hard to see how things fit together at all. Like this, the first sentence of John Milton's Paradise Lost:
Of Man's First Disobedience, and the Fruit
Of that Forbidden Tree, whose mortal tast
Brought Death into the World, and all our woe,
With loss of Eden, till one greater Man
Restore us, and regain the blissful Seat,
Sing Heav'nly Muse, that on the secret top
of Oreb, or of Sinai, didst inspire
That Shepherd, who first taught the chosen Seed,
In the Beginning how the Heav'ns and Earth
Rose out of Chaos: Or if Sion Hill
Delight thee more, and Siloa's Brook that flow'd
Fast by the Oracle of God; I thence
Invoke thy aide to my adventurous Song,
That with no middle flight intends to soar
Above th' Aonian Mount, while it pursues
Things unattempted yet in Prose or Rhime.
Wait. What? That's an awful lot of yammering just to get some muses to sing a little ditty. Also, that whole thing's a sentence? Yowza. But hey, Milton was famous for his slithering syntax, the longer the better.
But we digress.
Sure, syntax can refer to the order of words in a sentence, like Yoda-speak from the Star Wars movies: "A very important concept in literature, syntax is!" But, more figuratively, it can refer to the organization of ideas or topics in a poem, as in, "Why did the poet go from talking about his mother to a description of an ostrich?"
See, talking syntax can be just as fun as talking sin and taxes. Maybe more so.