Voyager is trapped in a dimensional void, where there are no resources of any kind, other than from other star ships who are trapped. Previous to Voyager's appearance, the law of the land was raid any new ship that appears, and fight it out yourself.
Janeway, using Starfleet principles, instead decides to create a mini star fleet, by convincing other ships to band together, share resources, in order to escape their situation.
It shows how the more aggressive species hurt this concept with their behavior, and why the joining of forces works well.
On top of that, it is a pretty exciting episode, with many good scenes, and satisfying from start to finish. One of the very best ST Voyager episodes.