A Pour-Over Will is a specialized Will that is used as a supplementary document to a Living Trust or Joint Living Trust. A Living Trust can limit which assets go through probate, but if any assets were not transferred into the trust, a Pour-Over Will serves as a safety net to convey those assets into the Living Trust so that they can be distributed with the Will writer's other assets in the trust.
Essentially, instead of the usual Will provisions that provide for the distribution of specific bequests, tangible personal property, and the residuary estate, the Pour-Over Will simply distributes the Will writer's remaining assets to their Living Trust, which then distributes everything in accordance with the provisions of the Living Trust.