Depends on the coverage you get but it covers most of the things that can go wrong on a holiday. Theft, injury, doctor bills, death, lost luggage, natural disasters etc.
It is HIGHLY recommended that you get it before you go. The small price you pay for insurance far out-weighs what it would cost to get a broken leg fixed overseas, buy all new gear or send your body home if you die.
One of God's own prototypes. Some kind of high powered mutant never even considered for mass production. Too weird to live, and too rare to die -HST