Wires
Wires are the middle pieces. They have varying functions and can do things in between inputs and outputs.
NOTE: The official name for bits with an orange color is WIRE
Wire
It goes between two bits and provides an extension. It allows you to place bits farther apart from each other, turn corners, and make connections that can twist, turn, and spin. It's just a wire.
Fork
It forks one input signal to three outputs. It can be used to send any type of signal.
Split
Similar to the fork bit, it splits one input to two outputs with an extension between each output. It can be used to send any type of signal.