B1- B2 Traveling Visas are two types of visiting visas. The B1 are meant for individuals who want to come to the US for a short-term business non-immigrant travel. The B2 visa is for people who may need to come to the US for a short time for medical treatment or other short time issues. To apply for this visa you have to go to the American Embassy or Consulate. To acquire the B1 you can get letter of recommendations of friends who plan to visit the US or have visited. However, for the B2 you need a statement from a doctor asserting that there is a medical problem and the individual is seeking medical treatment. Also, the individual applying for the B2 Visa must also have enough funding to support him self while living in the US because with the B2 Visa the individual is not permitted to work.

Links:

A thorough view of what is the B1 and B2 Traveling Visa.