Hi,
"Unique" will match with the last key into the lookup, then if you have several rows with the same key, this will the last will match.
Contrary to the "First match" which will match with the first loaded row into the lookup if several rows have same key.
"All matches" : if several matches are found in the Inner Join, i.e. rows matching the explicit join as well as the filter, all of them will be added to the output flow
