A quick goog search on "Edge Storage" and came up with this:
Edge storage or on-board storage means the video recording at the edge of the Ethernet network as opposed to transmit the data across the network. The edge storage is able to provide three main benefits; decentralized storage, redundancy, and low bandwidth. This is the reason why it's widely used in many IP cameras. Edge storage function enables camera to record video directly to a storage device such as an SD/SDHC card inserted into the camera. Additionally, it can store the snapshot either captured by motion detection or user's operation.
So, just another term for SD card to confuss old farts like me?
Thanks for the brief explanation, Nayr