It varies country to country, but in the United States, the average is this:
2 weeks per year after one year's service (but many companies let you "borrow" time before the one year is up) for the first 5 years.
3 weeks per year after five years of service.
Depending upon whether the organization is a large global one or a small mom-and-pop one, the amount of vacation benefit may vary.
Also, keep in mind that vacation is not a legally required benefit; it's a perk.