Energy or Power - Difference and how to consider them

I’m quite confused between Power and Energy in Home Assistant.
I have several devices that can monitor the consumption but not all of them provide the same info.

For example AUSS Plug provides only a Power reading
Shelly EM provides Energy and Power
while EM Pro provides a Power and a Total Active Energy

The Energy dashboard, I really love, works only on Energy so I have troubles with some of the plugs.

Can anyone help me understand better?

I think this discussion should get you started: Energy integration only used kWh, not kW? - #5 by petro