Confinement is the practice of putting a captive in a state where he or she has very little room to move. It is an extreme form of imprisonment. It may involve a very small cell or cage, a coffin or a body bag that is tied down.
It is not necessarily the same as strict bondage which, while restricting and inescapable, might stil allow the captive to roll around in a sizeable area. The captive may or may not be in bondage or tethered in addition to the confinement.