Purim celebrates the victory of the Jewish People and the downfall of Haman.

In this address, the Rebbe speaks about the relevance of the Purim story to every Jewish child:

Haman represents the Evil Inclination; he tries to persuade Jewish children to imitate their non-Jewish neighbors, and not to stand out as different.

But the Jewish child boldly rejects his advances, and in the end, his mischief only causes a Jewish child to attain even greater light, joy, gladness, and honor, just as in the Purim story.

The message of Purim is: No Haman and no Evil Inclination has any control over us.