That is part of an add-a-zone module kit. You will need it! That splits one of your wires to two out in the field. There is another module in a valve box out in the yard somewhere. You’ll need to remember which wire the orange was connected to at the controller.
What this means is, a wire went bad and the last irrigator couldn’t find the break and adding a new wire was too costly or a zone valve was added and they used this instead of running a new wire.
Here is a link where you can learn about it: Add-A-Zone info
Welcome to the neighborhood!