The audio signal is what comes out of the TD-10 module. Meaning you want to record the sounds you have into GarageBand. All this would require would be a USB audio interface to get your stereo 1/4" output of the TD-10 module into the computer so you can record those audio signals into the computer.
The MIDI jack is the funny connector on the TD-10 module that has five holes arrayed into a smiley face. This means you want your V-drums to trigger other sounds in GarageBand (you're not recording the sound of the TD-10 module, but the data of your performance). This data can then play other sounds, for instance, the sound of the drums that live within GarageBand. To do this, you would need a MIDI-to-USB interface. You would play your Vdrums, but the sounds would be coming from your computer, or something else. You are not recording the sounds from your TD-10 module.