In the Japanese martial arts, an uchi deshi (live-in student) is a student or group of students who have an additional responsibility to the dojo.
As with most things in the martial arts, those looking from the outside will find things a bit strange, but when understood from the context of the dojo and how the art is transmitted, the functionality makes complete sense.
Often at the start of the class one will see the students of the dojo setting up and getting everything ready for the arrival of the teacher. Mats put out, training tools arranged, and making sure the dojo is in order.
We also see the opposite after class with the students in the dojo putting everything away, cleaning the floor, and making sure closing down is in order.
One of the reasons for this is the value of time.
What the teacher has to share, that transmission, is limited to a few hours a week.
Any time spent *not* teaching or sharing is wasted opportunity.
For this reasons everything that is needed or might be needed for a class- questions do come up, is ready right away.
As an uchi deshi this concept is taken a step further.
Uchi deshi are live in students in that, depending on the dojo-situation, might stay over or live at the dojo full or part time, or spend extra time at the dojo assisting in running it, in order to free up time for the teacher and senior students to teach more.
This exchange, as an uchi deshi might include extra training with the teacher or seniors, and/or the value in being able to watch the teacher and seniors outside of regular class and teaching.
A chance to see how a martial artists conducts themselves, or for additional insights with training by just *being* around.