GIS Match Codes

#1

I’m struggling to understand what these match codes match to-- zip codes? FIPS? Where can I find documentation to interpret them as geographic locations.
Thanks in advance.

#2

The geographic codes in the microdata available via IPUMS Terra correspond to the data available via IPUMS International. So, for example the GEO2_US2005variable indicates the PUMA (or public use microdata area), which is the second level of geographic identification available in US samples. A complete listing of all geographic variables available in IPUMS International (and by extension IPUMS Terra) is available here.