Simple questions, I hope...

I've been told by the powers that be to build/buy/steal a garden gate
and fit it.

So in my wisdom I've decided to build one, that way I get to decide how
tall, how thick etc...

The timber merchant has 5" and 6" T&G flooring which I assume, with
suitable preservative treatment, will be OK?

Also, what's the difference between whitewood and redwood?
--
Clint Sharp