§1. In law, the term pious foundations includes: 1/ autonomous pious foundations, that is, aggregates of things (universitates rerum) destined for the purposes mentioned in can. 114, §2 and erected as a juridic person by competent ecclesiastical authority; 2/ non-autonomous pious foundations, that _is, temporal goods given in some way to a public juridic person with the obligation for a long time, to be determined by particular law, of celebrating Masses and performing other specified ecclesiastical functions or of otherwise pursuing the purposes mentioned in can. 114, §2, from the annual revenues.
§2. If the goods of a non-autonomous pious foundation have been entrusted to a juridic person subject to a diocesan bishop, they must be remanded to the institute mentioned in can. 1274, §1 when the time is completed unless some other intention of the founder had been expressly manifested; otherwise, they accrue to the juridic person itself.
Source: Code of Canon Law (Vatican.va)