The idiom "If and when X, (consequence)" has the meaning "if X happens, then when X happens, (consequence)". In other words, the "(consequence)" will not happen unless X happens, and will not happen before X happens.
It is generally used when talking about not making unnecessary preparations for an event that may not occur:
We'll come up with a zombie attack mitigation plan if and when we're attacked.
Some people might complain that "if and when" is redundant, because the "if" carries with it a sense of "when", in that you don't know whether X is going to happen until it actually does. But it's sometimes possible to know to some degree of certainty that something is going to happen, before it actually occurs - and in fact this is often the situation where the phrase is used:
We'll open fire on them if and when they open fire on us.
Simply saying "if they open fire on us" can invite the response "but we know they're going to, so we should fire now"; the when emphasises the speakers view that no pre-emptive action should be taken.
As to the difference between "if and when" and "when and if", the basic meaning is identical (as others have noted), but there is possibly a slight difference of nuance: the standard phrase is "if and when X", but inverting it to "when and if X" emphasises the if part, thereby putting more emphasis on the fact that it is uncertain whether X will actually occur.
You asked for an example; here’s a classic. The teacher gave an assignment to write an essay. A student asked, “How long should it be?” The teacher responded,
The same as a woman’s skirt –– long enough to cover the subject, but short enough to keep it interesting.
Best Answer
Watercooler chat is the informal chatter that occurs in offices. It's where gossip is traded, sporting teams are discussed, and weekend and after-work plans are made.
Cool kids (in this context) would refer to the people in your workplace who are particularly smart or funny; the people you would like to impress.
To extrapolate: the cool kids around the water cooler are the people you want to impress in a social or informal way at your workplace.
To extrapolate further: when you’re talking to the cool kids around the water cooler you would want to make sure you're using the correct terminology, in order to be perceived by the said "cool kids" as clever.