Channel between foundation wall and floor in crawlspace
It appears to be a drain channel as part of a groundwater mitigation system. Most water enters a basement through the area where the floor and walls meet, and this would carry that away, presumably to a sump pail. I can't tell you what brand yours is, but a search reveals many similar products. 

The bottom plate of the wall is wrapped to minimize moisture absorption and transmission. Whether the channel was installed at the time of initial home construction or later is unclear. I can imagine a solution where channel is installed on top of an existing slab and a thin layer of cementitious material is poured inside it to raise the slab level accordingly.