I've never heard a name for it, but as to the second part of your question: I'd say that, like many literary devices, it can be done poorly, but if used well it can be a great asset to a story.
Let's say that there is some background information that you need to convey to the reader. Whether it's a detail about how the police department files DNA samples, why Uncle Harry and cousin Sally can't be invited to family gathering together, or how Trantor came to be the capital of the Galactic Empire, there are some facts that the reader may need to know to understand the story that happened before the story began or that are background that the main characters all know. How do you convey this information to the reader?
BTW I think this is especially a problem for science fiction and fantasy stories where there may be a whole history and culture that the writer has completely invented and that the reader cannot possibly be expected to know. In a conventional contemporary novel, if I was writing that the hero decided to travel from Los Angeles to Paris, I wouldn't think it necessary to explain that these are two major cities in two different countries, that the people there speak different languages, etc. But if in a science fiction story I said that the hero travelled from Dorsai to Kultis, I might need to give a lot of background for events to make sense. To a lesser extent this is also an issue for historical fiction or stories set in cultures that are real but unfamiliar to the reader. Like a story for American readers that is set in Russia might need to explain aspect of Russian culture.
But anyway, how to convey such information?
1. Have the characters tell each other things that they all already know.
Often this comes across as really lame. Like, the first officer of the star ship says to the captain, "We're approaching the planet Trantor. That's the capital of our empire." Like, duh, does he really need to tell him this? Can one become a captain of a powerful star ship and not know what the capital of his own nation is? I've heard this called, "as you know dialog", because it often begins with a character saying, "As you know ..."
That said, sometimes you can slip some fast facts by this way if you word it right. Someone might say things that everyone around him already knows as a general complaint, or to point out that this fact is relevant. Like, "What time is it now? Do we have time to sneak out and return before the boss gets back at 3:00?" A sentence like that could convey what time the boss will return and also the implication that the characters will get in trouble if they're not back by the time the boss returns, even though these facts are likely known to all the characters, without sounding obviously pointless. Or, "Blast, we'll never get this done in time! It takes two weeks to get a DNA test back from the lab!" All the characters might be expected to know how long the lab takes, but it's not unreasonable that someone would say that in the course of making the point that it's too long to be useful. You may be able to just add a few extra words that are technically unnecessary but not obviously ridiculous. Like, instead of having a character say, "I saw Sally yesterday", have him say, "I saw your daughter Sally yesterday". Now the reader knows that Sally is the other character's daughter. The statement isn't obviously ridiculous -- we might even say that in context he might well have said "daughter" to avoid confusion with some other Sally.
2. Narration. You can interrupt the flow of the story to give some background. Like, "'I suppose we have to invite Uncle Harry,' Bob said. No one wanted to invite Uncle Harry. He always showed up drunk and embarrassed everyone." Etc. In my humble opinion, writers are too quick to avoid this method. Yes, it violates the classic "show don't tell" and it interrupts the action. But if done right, it can get a bunch of background material in quickly and efficiently without having to come up with contrived reasons for characters to explain things to each other.
3. The uninformed person. Include a character who doesn't know things that all the other characters would likely know, so that people have to stop and explain things to him, and thus, to the reader. As Lauren Ipsum says, this person doesn't have to be portrayed as stupid, just uninformed. Life if you need to explain family history, have a character bring his new girlfriend to a family gathering so he has to explain things to her. Instead of the doctor explaining medical procedure to another doctor who would likely already know it, have him explain it to the patient's brother. Etc.
I've seen this done lamely, like if it's clear that the ONLY reason this character is here is so things can be explained to him. I just saw a fragment of a science fiction movie the other day that has scene early on with a teacher giving a history lecture to her students. I didn't watch the whole movie as it was kind of lame, and that was an example of the lameness: As far as I could see, the class had nothing to do with the rest of the story, we never see them again, it was just an obvious device to get this background material in.
But when done right, it can be seamless. Make the uninformed character an important character in the story, someone who has a reason to be there other than to be ignorant. Make his ignorance natural and understandable -- he's not a doctor, he's not a member of the family, he's from another planet, whatever -- so that the reader isn't left thinking, "How could this person even survive if he's so dumb?" And in general, break the explanations up into small pieces. Don't have someone give him a two hour lecture on the history of the world. Have one person explain this relevant point to him and another person explain that.