Visa and passport are important traveling documents because they determine whether or not you are allowed entry into a foreign country. The visa will also state entry conditions for foreigners and is usually authorized by stamping it in your passport.
Passport services you are likely to require include new passport acquisition, renewals, extra blank pages or additional issuances. There are different kinds of visas as well depending on purpose of visit and the country you are visiting. You may need to get a new visa, update or change the one you already have.
Passports services are normally provided by the immigration department of your country, embassies or consulates if you are in a foreign country. Visas, on the other hand, are provided by the consulate or embassy of the country you intend to visit or you could get one upon your arrival in the visiting country. Authorized international travel agencies also offer passport-visa services though their processing charges are often higher.
Check Travel.State.Gov for more information