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Usually anything that powers the IC, powers a transistor/MOSFET or supply power to drive a high current component is considered the power net.
Signal nets are somethings that carries smaller current to turn on transistor/MOSFET gate, logic decision taken by a IC, or basically any signal that carries information is considered as the Signal net.
According to your attachment :
- VDDA, VSSA, VDDB, VSSB, +5v, GND can be considered as power nets
- Disable, PWM signals can be considered as signal nets