What's the name of the thing next to the ignition coil of Yinglang gt? It is round, with one end connected to a cylinder and one end plugged with a wire.

Is the ignition coil connected to the engine?

If it is, it is a high-voltage line. One end of the high-voltage line is connected to the high-voltage output end of the coil, and the other end is connected to the spark plug.

There is also a low-voltage docking harness, which is used to connect the battery and the ignition coil, also called harness plug/terminal.