(This is a summary from several sources and was the product of the enlightenment of my own ignorance on the subject.  So please feel free to comment and or correct!  Quotes taken from several sources that will be listed at the bottom of the post)

Found in the document “Presbyterorum ordinis“, a product of the Second Vatican Council, we find the origins of a Personal Prelature (PP).  The PP is comprised of a hierarchy (a prelate, priests, deacons and sometimes lay faithful) and is established to carry out a specific pastoral function for the Church.  The “Personal” refers to the jurisdiction of the SSPX would have.   Unlike a diocese, their jurisdiction is linked to persons as opposed to any particular territory.

The personal prelature is similar to a religious order, in that  “the prelate governs the prelature with ordinary power (that power given to those who hold a valid office and may execute Church law) and is selected according to the statutes of the prelature (can. 295), which could mean election by the members of the prelature or some other method.  Also, the clergy of the prelature are incardinated into the prelature itself as opposed to the local particular church (dioceses).”  For those of us unfamiliar with the term incardinated, it refers to the fact that no priest functions without a head, be that a bishop, superior or in this case a prelate.

Where the PP differs from a religious order is that they don’t take religious vows, they may have a different relationship to the local ordinary (i.e. they may be exempt from the laws and the governance of the particular church where they live and work, which might be good in the DoR), the prelature defines its own relationship with the laity dedicated to its mission and finally the prelate may be a bishop which generally doesn’t happen in religious order.

The personal prelature is also different from an ordinariate that, is technically a diocese of persons rather than being defined by a  geographical location.

An example of a personal prelatures in the Church is Opus Dei

The good news, in my view, is that we may soon be able to apply the above to the SSPX.

Sentire Cum Ecclesia,

JBC

Source 1, Source 2, Source 3 (For those academics among us, don’t judge me for using Wikipedia.)

(Edit: Pope Benedict XVI’s provision for the Anglicans is actually a personal ordinariate.)