"Darmok" is an episode of Star Trek – The Next Generation first broadcast in 1991. The exceptional thing about this episode is that the universal translator, the "magic" device they have that instantaneously translates between any two languages, doesn't work. Or rather it works more as we'd expect it to work, it translates words, but the sentences themselves don't make much sense.
If you haven't seen the episode, I suggest you watch it. I think it's better to watch it before reading the rest of this post. This not so much a spoiler warning for a 24 year old episode, as it is a recommendation.
The gist of the episode is as follows: the Enterprise rendezvous with a Tamarian ship. So far the Federation has not been able to communicate with Tamarians. On the main screen the Enterprise bridge crew can see the Tamarian bridge crew argue using what seem to be very odd sentences. Then the Tamarian captain takes a knife, de-materializes (apparently transported), and Captain Picard also dematerializes (with the Tamarian transporter effect), and both are beamed by the Tamarians to the planet. Additionally the Tamarians set up a force field to prevent the Enterprise from beaming up the Captain, or from beaming down anyone else.
On the surface of the planet, Picard gradually learns to understand the other captain's attempts to communicate in metaphors. He also learns that he was brought there so they could play out one of the stories told by those metaphors. The story of two strangers who arrive at an island and become friends after fighting a common foe.
Meanwhile on the Enterprise the crew tries to figure out how to get the Captain back, and to that end they try to figure out the discussion from the beginning of the episode. Data at first notes that they're using proper names of people and places, and figures out that these are metaphors. However, not knowing what they're metaphors for, that still leaves them unable to interpret them.
On the planet Picard and the Tamarian captain fight a common foe. The Tamarian captain dies, which makes the current story different from the story the Tamarian chose for the encounter. The Enterprise manages to beam up Picard as things heat up between the two ships just in time to use his new knowledge of Tamarians to communicate to the Tamarian first officer what happened on the planet. The Tamarian accepts the story and "names it" "Dathan and Picard at El Adrel." and also uses a variation on one of the metphors, showing this way of communications is more flexible than it might have seemed at first.
The epilogue for the piece shows Picard reading Homer, explaining to Riker that by knowing our own stories (cultural metaphors) betters, we may have a better understanding for other cultures.
Almost a decade ago, but still closer to the time of this posting than to the original airdate, the linguistics blog " Tenser, said the Tensor – Darmok" wrote a post about the episode explaining that from a linguistics POV it doesn't make sense. Then he goes to explain why a language and a culture built entirely on metaphor don't make sense.
I've seen other criticism along the same lines, but the Tenser's blog post is a comprehensive explanation of this particular reaction.
I think that criticism misses the point. The last scene, Picard reading Homer, helps to point us in the right direction.
We also speak using metaphors, allusions, idioms, many of which don't make any literal sense. We use them so often and so naturally, and nowadays may even pre-pend some of them with the word "literally", that we don't even notice that. Read any newspaper (or news site) and see how many metaphors you find. Translating them a literal translation to a different language would make them sound as odd as some of the sentences used by the Tamarians.
The common references, metaphors, allusions are our culture. Translators deal with these issues on a daily basis, and not just literary translators. Translation is not just about language, but also about culture. An idiom that makes perfect sense in one language, is completely opaque in another, and in translation may need to be replaced by another idiom with equivalent meaning in the target language/culture.
I'm not ignoring the fact that the Tamarians in this episode took the cultural metaphor further by actually re-enacting it. Within the story, it emphasizes the important role of metaphors in communications. Cultural metaphors are significant in Earth cultures as well.
The story is about communicating with a person from another culture. It's also about respecting the other culture as you respect your own. Each culture has its own allusions, and they're equally valid. The aliens, in this case the Tamarians, are stand-ins for foreigners, without naming any existing Earth culture.
Thus, while it may cause a few raised eye brows among linguists, it makes sense from a translator's pov.