What is a K-3 and a K-4 visa?

Question

all the technical talk doesn't make any sense at all to me please help

Answer 1

K-3 is for a foreign spouse of a US citizen or permanent resident.  K-4 is for the spouse's children, if any.

K-4 could also be for the children of a foreign fiance/fiancee.  K-1 is for the fiance/fiancee.

Answer 2

A K-3 is a non-immigrant visa for the spouse of an American citizen, who has had an IR-1 immigrant visa petition already filed for them. The K-3 was established when INS/USCIS was having lengthy delays in processing the immigrant visa petitions. As the K-3 is non-immigrant petition the processing time was supposed to be faster so the K-3 was intended to be used while waiting for the immigrant petition. And so it was, for a while. These days there isn't all that much difference in processing. The K-4 is the same thing for the minor children of the K-3, but it doesn't require an immigrant petition filed before it can be approved and used.