A man is dealt a poker hand (5 cards) from an ordinary deck. In how many ways can he be dealt

(i) a straight.

The answer in the back of my book says (I know 40 is deducted from the number of straight flush, but I don't know what the is.

(ii) a pair of aces (I could not find the poker rule for this, so have no idea what this is)

The answer provided was ( again I do know what the reason is for )

I have never played a card game, and know nothing about poker. I understand it would be tough to explain these to me, but I would appreciate the time and effort that you give me.