There are multiple scenarios you use inputlookup
For example:
1. | inputlookup <lookup file> This just outputs the content of the lookup file
2. <your search> |inputlookup <lookup file> append=true This appends the content of your lookup file to the end of your search results
You can view more examples here - https://docs.splunk.com/Documentation/Splunk/8.0.0/SearchReference/Inputlookup
Cheers
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