If you're looking up a term in German, say, on the Web and you want to know what it is in English, it's like looking up a dictionary: you want the English term in the particular subject you are interested in. You don't necessarily want a lot of text as that is more of a distraction than a help. If the search throws up a German/English glossary on the topic you are interested in, and containing the terms you are looking for then that is a great help. If the search throws up texts in German containing the terms you are looking for, then it is often difficult, if not impossible, to find the English translation for the text, and you will have to search for a text that is about the particular subject you are dealing with, which is also quite time consuming.
I think that keywords are knowledge holders. A glossary of terms on a subject is condensed knowledge of that subject. It is a list of substantives, mostly.