A redirector is created any time an object is moved in your content browser that is referenced by another object/actor. A material that is being used by a static mesh is a good example. The static mesh is looking at a specific location for that material (the location it was at when the static mesh had the material assigned to it), and if the material is moved but the object not told that it has been moved, it can break the mesh. Redirectors are put into place to prevent that break from occurring. Think of it like a signpost that says "Not here anymore, try this location instead: ". These are not meant to be permanent solutions and I actively encourage developers to add assets into the folder they are going to remain instead of moving them about. Otherwise, the options are to fix up redirectors, or re-reference the moved asset (in this case, the material) wherever it is referenced (the static mesh) and manually delete the redirectors. You can do this by going to Windows Explorer and finding the filepath:
\Unreal Projects\PROJECTNAME\content\
Once there, find the original location of the object and there should be a small file acting as the redirector for the asset. You can manually delete that. Any folders with no information left in them (all redirectors have been deleted), will not show up in the content browser. I will repeat, however, that it is absolutely imperitive to re-reference the assets manually if you do it this way. There are times that this can cause extremely averse effects or crashes due to null references in structs/blueprint actors.
I’m not entirely certain what is going on there, xuri. I attempted to reproduce it on my end but was unsuccessful. What version of the editor are you using and what specific steps did you take before that folder was created?