Traditional and virtual phone numbers follow the same format. A standard US telephone landline number is made up of 10 digits. The first three digits represent the area code, which is assigned to a local part of the country.
Traditional landlines follow this strictly, but virtual phone services don't. In fact, you can create a virtual presence in a certain locale by purchasing a virtual phone number with its local area code even if you do not have a physical address in the area.
The first three digits could also identify it as a toll-free number. The most popular toll-free prefix is 800, but there are other toll-free prefixes available like 888, 877, 866, 855, and 844. If you are looking to build a national presence, this option is better for your business.