All the connections (grnd, left, right) are on the center shaft.
from the tip end, the tip is channel X, the next ring is channel Y and the base is the ground.
X vs Y? one is left and the other the right, but it all depends where the other end of the wires end up.
When working with stereo, it is best to use a braided covered, two wire leads of different colors ( copper & silver are typical). The braided shield is the ground and that must be connected to the base and at the remote end also to ground connection - - this is typically where it goes awry.
Technically, there's are true left/right channels in the circuitry and by rights those signals should come all the way thru to the speakers / headphones - - but unless you fuss with testing left, then right, you'll never now the difference. If you have to have it right, then at the remote end, just swap where the leads were attached.