The outer tie rod is the tie rod with a bearing that connects to the wheel and the inner tie rod connects to the inner part where it connects to the steering linkage.
The other tie rod will always be on the furthest end of and connecting to the wheel to allow the wheel to turn while the inner tie rod will be connected to the other tie rod but be on the inner side.
Here's an image showing what the inner and outer tie rods are.
The inner tie rod connects to the outer tie rod but the outer tie rod connects to the wheel assembly but the inner tie rod connects to the rest of the steering linkage.