I-797A: approval notice for change of status
(new I-94 is attached to the I-797A)
I-797B: approval notice for consular processing
(no new I-94 attached, need to apply for a new
visa outside the U.S. and seek entry at border)
I-797C: fee receipt and other notices that are
not approval notices
I-797D: approval notice for certain USCIS-issued
cards such as the GC or EAD card