Normally Open, Normally Closed.
When the relay coil is not energized, terminal 87A is connected to 30. When you power the relay coil, terminal 87 connects to 30 and 87A opens. This is why it's known as a SPDT, Single Pole, Double Throw. 'Normally' is a term to describe the relay in it's unpowered configuration, think of it as the resting state.
As an on/off (relay #1), you use hot to 30 and switched load to 87.
Connect 87 on relay #1 to 30 on relay #2.
As a high/low (relay #2), you put low beam on 87A and high beam on 87.
Or in your described system, you would just use terminal 30 to the kill-switched lighting and your switch would toggle between high-low rather than on-off.
Substitute AUX Light for low and FLUSHMOUNT for high beam.