Wow! 10 views so far, and nobody wants to be the first to step into this minefield. Here's a first shot (rather from the hip).
The second syllable of syntax is a clue to its relationship to the word 'tactics'. It's the order that you put words in, much as a tactician deploys troops for various effects.
'Grammar' has widely differing meanings - particularly descriptivist (the way things are in fact) and prescriptivist (the way someone thinks things should be.
A descriptive grammar specifies a syntax for any particular language - the way words are actually put together to convey meaning. A prescriptive grammar prescribes a syntax (the way sentences should - according to a fairly random set of 'rules' - be put together).
b (adopting foetal position and logging off immediately)