What is the meaning of "ground" and "-V" in a simple push-pull circuit?
When using a 'split rail' like this, ground will be the mid terminal of the battery or power supply. So if you had a +12v and a -12v supply, that would need two 12v batteries, connected in series, with their mid point taken to be ground.

This split rail connection allows you to generate both positive and negative voltages into the load. Your motor would connect between ground and \$V_E\$. This would allow it to be driven in either direction.