A toll-free number is one that starts with a toll-free area code: 800, 888, 877, 866, 855, 844, or 833. When someone dials one of these numbers, they aren't charged for the call. Whoever owns the toll-free phone number pays instead.
Toll-free phone numbers can be random digits or even words – numbers that use words (like 1-800 FLOWERS) are called vanity numbers.
Numbers with the 800 prefix are considered premium toll-free numbers and are typically less available than other prefixes.