What is the difference between sink and slack?

Hi all,
i have a question regarding sinks and slacks. For me is not clear what is the difference between the two of them.
My understanding is the following:
Sink is used to define the demand or excess of energy, it goes only in one direction.
Slack is used to balance the buses, it can either receive or provide energy.
Is this correct?
How can i integrate a slack in oemof?
I haven’t found anything helpful in the official documetation.

Hi Roberta,

If you want a slack, you should be able define a slack bus by Bus(label="slack_bus", balanced=False). It’s hardly ever done, so please report your experiences.

PS: However, separate sink and source have the advantage that you can avoid closed loops in the directed energy system graph. So, they might (possibly) lead to an improved computational performance for solving.