When troops are sheltered under canvas (in tents), they are in camp.

When they are resting on the ground without tents (for instance, on the

firing line the night before or during a battle), they are in what is

called bivouac. When they occupy buildings in towns or villages, or huts

especially erected, they are in cantonment. When they are assigned to

public (such as post-offices, town halls, court houses, hotels, etc.) or

private buildings they are said to be billeted.