What is the difference between a machine readable passport, a biometric passport and an e-passport?
 -A biometric passport is a passport that has a digital photo instead of one that is glued on.
  An e-passport has a micro-chip that can be read by special equipment to confirm the data printed on the passport.

My passport has expired or been damaged. However, I still have a valid U.S. visa in the passport.
What should I do?
 -If the photo page on your passport has been damaged (e.g. has become detached, or looks like it may become detached, from the rest of the passport), please apply for a new visa in a new passport, submitting both the damaged and new passport in support of your application.
 We cannot place a visa in a passport with a photo page that is even partially detached.
  If your passport has this problem, please apply for a new passport before submitting your visa application.
  If the passport has expired, and you still have a valid visa, you may travel with two passports, i.e. your old passport with the visa, and your new passport, or apply for a new visa in your new passport.
  Please note that you cannot transfer a visa to another passport.

I have a visa in my old passport. Can I just transfer it over?
-It is not possible to transfer a visa from one passport to another without making a new visa application.