there is just VCC , VDD, VPWR etc... that's why i was asking for the differenceThose are just names, and they need to be defined/documented somewhere.
Sometimes "knowing" that Vcc is usually +5V, might not be enough, or using the name/label '+5V' might not be enough, because there may be more than one 5V supply and you need to know which 5V supply is connected to which IC. (i.e., you might have Vcc1 & Vcc2, etc.)
It's like anything else on a schematic... It helps relate the schematic to the physical circuit.
Typically with an emulator/simulator, you can assign connections/meanings of your choice to these names/symbols.