How does Kipling characterize the colonized people?

According to Kipling, why is it appropriate to describe imperialism as a “burden”?

Despite the burden, what does Kipling say the reward will be for the colonizers?

Take up the White Man's burden—

Send forth the best ye breed—

Go, bind your sons to exile

To serve your captives' need;

To wait, in heavy harness,

On fluttered folk and wild—

Your new-caught sullen peoples,

Half devil and half child. . . .

Take up the White Man's burden—

The savage wars of peace—

Fill full the mouth of Famine,

And bid the sickness cease;

And when your goal is nearest

(The end for others sought)

Watch sloth and heathen folly

Bring all your hope to nought. . . .

Take up the White Man's burden!

Have done with childish days—

The lightly-proffered laurel,

The easy ungrudged praise:

Comes now, to search your manhood

Through all the thankless years,

Cold, edged with dear-bought wisdom,

The judgment of your peers.

Source: Rudyard Kipling, “The White Man's Burden,” McClure's Magazine, February 1899, 290–91.