The process being observed in this experiment is diffusion (the movement of molecules from an area of high concentration to one of low concentration).
For instance, if you have carried out an experiment similar to the one described in the question above, then you will know that the dialysis tube is placed in a container that has water and which is set up in the following way:
The dialysis tube contains starch solution (in some cases, it might even have glucose solution too). Meanwhile, the water outside the dialysis tube (which is placed in a container) contains starch indicator (which has an amber color). Moreover, this experiment is basically meant to show how diffusion works.
For instance, after a while, the inside of the dialysis tube will turn black as the starch indicator in the water will diffuse into the tube (however, the glucose solution doesn't diffuse out, it remains inside).
In other words, only the starch would able to diffuse because the dialysis tube is semi-permeable ( meaning that only specific substances are allowed to pass through the tube, in this case the starch was able to, but glucose wasn't).
Here is a diagram of how the experiment set up looks like.
In case you want to test your knowledge, here's a question that comes from the Regents:
What will the solution in the beaker and the tubing look like after 20 minutes?
The indicator solution in the beaker will be blue black and the starch solution in the tubing will not change color.
The starch solution in the tubing will be blue black and the indicator solution in the beaker will not change color.
Neither the indicator solution nor the starch solution will be blue black.
Both the indicator solution and the starch solution will be blue black.
Here's the website from which I got the question from, in case you want to practice:
The answer to the question is choice (2).
Also, for your reference, the starch solution indicator is also known as Lugol's Iodine solution (and as you might have guessed, it tests for the presence of starch).
Hope this helps! :-)