Your Open Question: What do people mean by push DOWN with your diaphram for support?

Does that mean to keep your belly expanded? Or does it mean to physically push down, as if defecating? I have heard the expression many times, but I dont understand. Below is an example i was given that I copied and pasted. As your notes get higher, push DOWN with your diaphragm; this is called being "grounded." To hit the high notes, you need to train your body to draw lower into your breath support. Imagine roots coming out of your feet and growing, digging deeper and deeper into the ground. Imagine you drawing your sound from those roots, going lower and lower as the notes get higher.