It sounds like a poorly worded question.
However, if I were to guess their intentions, they might be interested in whether the journal appears in the "Science Citation Index - Expanded" or "Social Sciences Citation Index". Or another influential one is whether it is in the Proquest index.
The reason I say this, is that inclusion in these indices are sometimes used as a minimal criteria for legitimacy as a journal for inclusion in world rankings.
E.g., The Shanghai rankings use:
ARWU uses six objective indicators to rank world universities,
including the number of alumni and staff winning Nobel Prizes and
Fields Medals, number of highly cited researchers selected by Thomson
Reuters, number of articles published in journals of Nature and
Science, number of articles indexed in Science Citation Index -
Expanded and Social Sciences Citation Index, and per capita
performance of a university. More than 1200 universities are actually
ranked by ARWU every year and the best 500 are published.
You can search for inclusion in Science and Social Science Citation Index here.