What is a spousal affidavit that relates to a South African life-partner visa application?

A spousal Affidavit is a sworn document stating that the South African citizen or permanent residency holder and the foreign partner are in a permanent relationship and for how many years.  This document is submitted as part of the proof of the relationship.

This document is in now way legally binding (like a marriage certificate); this is only swearing an oath that the couple is currently and has been in a permanent relationship.