cc is displacement and therefore more or less the approxiamte size of the engine.
on a chainsaw, it's important to know how big (aka heavy) and how powerful a motor is, since it could be a safety issue.
on a bike motor, displacement approximates the power if the engine is not tuned unusually, but only to a certain degree. a 49cc scooter may go 35mph and a 110cc one may go 45mph, but a 250cc bike can go 95mph if tuned well so thats not a power rating, just a basic guideline based on engine displacement. insurance on bikes is generally based on cc's of the motor. they know a 1000cc is more likely to be crashed at speed than a tiny scooter from the available power and the temptation to use it.
some more examples:
49cc scooter: about 4.5hp max stock
100cc scooter: ~8hp
harbor freight 6.5hp = 200cc
HF 13hp = 400cc
average 400cc outboard = only 10hp
average 800cc outboard = only 30hp
kawasaki ninja 600cc bike = ~125hp
1200cc sports bike = ~180hp
1000cc (1L) 3cyl geo metro = 45hp
my kawasaki 550cc jet ski = 39hp
so thats kind of a long way to say its very much a relative thing. i've seen tiny motors make huge power, and giant motors produce barely anything like those 80's cadillacs.
also as a side note, the rev range on motors also widely varies. geo metro tops out around 6000 to 7000rpm, the stock HF 6.5hp is 3600rpm, my jet ski is around 6000, and the ninja 600cc is an insane 16 000 to 20 000rpm
