According to the sages, Yehoshua/Joshua composed this prayer upon entering the Holy Land. The great Kabbalist, Rabbi Yitzchak Luria, the Ari, writes that this prayer contains within it greater praise then the entire prayer service.

Aleinu secures the prayers so that none of the energy of our prayers become a source of anything unholy. For example, our elevated rapture does not evolve into anger.

Aleinu is more than prayer, as it also serves to help smooth the transition between prayer and our movement outward into the world. It assists us in rejoining the world, and that is why it is said at the end before we leave the synagogue.

Concluding prayers, we journey into the world with the recognition that “there is nothing else” besides Him. Realizing this allows us to see the hand of the Creator in every step we take, and as a result, our lives become more Godly and less mundane, more spiritual and less materialistic, and more profound and less petty.