36-pin Stacking header pack of 5
Headers are like the duct tape of electronics. They're great for connecting things together, soldering to perf-boards, sockets for wires or break-away header, etc. We go through these guys real fast, and thought that given how handy they are, we'd offer them in a pack of five!
Stacking headers are a twist on the standard/common male and female header sets. In this case you have one header that has a socket on one end, and a long tail that gets soldered through a PCB. When soldered into a through-hole pad, the long tails can plug into another board's female headers while the sockets above the PCB allow another board to be plugged in. This means you can stack PCBs, as many as you like, on top of each other. You can even plug the lower board into a solderless breadboard, or plug wires into the top board's sockets.