What is a Unit Load Device (ULD)?
A device used to load freight onto an airplane. Using a ULD, multiple pieces of cargo can be packaged together for faster, more efficient loading. Aircraft are designed to hold ULDs in place with built-in loading and restraint systems.
There are two kinds of ULDs: aircraft containers (also called cans or pods - these are structures with walls and lids) and aircraft pallet/net combinations (cheaper but a bit less secure than containers).