If you are trying to get a broad view of a topic, or are not sure of the words you should use, browsing the codes is your best bet. You may also want to go here to get a more thorough explanation of the codes: 

Just as in any set of primary sources, users need to be aware of the strengths and weaknesses of this selection. 

It is best at  telling us about the particular concerns of ethnic communities, what information was important to the U.S. Government, and the priorities of the Chicago school of sociology.  There is an emphasis on communities from Eastern and Southern Europe,  with less information about those from other parts of the world.

Researchers should also understand that the translations in CFLPS were done years or even decades after the publication of the original articles.  Translations, often done by people within the neighborhoods and groups that were described, may have been biased to reflect well on those communities.