Overlaid
All the signals selected are shown together. Selecting one of the two signals displayed (Trace 1, Trace 3, or Trace 4, in this example) will bold that signal line and display that signal's Y-axis units on the left.
By unit
Signals that use the same measurement unit (for example, bar, %, etc.) are shown in panels together.
Separate
Each signal is shown in a separate panel.