On diagrams you'd use + as the "source" of elecricity, i.e. you assume electricity flows from + to - (poaitive to negative). Electricity as far as physics goes is an effect created by electrons, which are defined as negative in charge.

DC is electricity where the literal flow of electrons from point A to point B make the current (so it flows from negative to positive, since it's the flow of "negative" electrons that carries electricity). Benjamin Franklin assumed logically that electricity obviously must flow from positive to negative (since it's the logical choice), but alas, he was wrong as far as history sees it. So today, whenever you're dealing with electrical diagrams current/electricity is assumed to flow from + to - while in the physical domain it's the negatively charged electrons that create what we call electricity.

AC is a bit different - here electrons aren't flowing directly from point A to point B, but rather wiggling about or "alternating" in place and it's this alternating movement that carries the (still negative) charge. But even for AC it still holds true that electrical charge is the "negative" charge of electrons and that this movement of electrons alternating in place enables them to move this "negative" charge of theirs from one place to another.

I assume you know about the saying "opposites attract" - for electricity and charge it's literally true, so you can view power consumption as the "positive" charge of protons (which is immovable because protons are bound to the cores of their atom), while it's the "negative" charge of electrons which are located in the outer shells of metal atoms that can leave their atoms and move their charge that are viewed as the source/carrier of electricsl energy.

I put negative and positive in quotes because to get back to your question about defining why Franklin was wrong:

As it stands, there are two conventions on electricity. One is used in diagrams and often attributed to Franklin, the one that says that electricity flows from the positive (+) to the negative (-) pole. The other is the physics convention that protons hold positive charge while electrons hold negative charge, and this is where the disparity comes from. I don't know which convention was chronologically earlier, but I assume it's the physics one since Franklin is the one cited as "wrong".

Obligatory I'm not an electrical engineer - this is only what I remember from my physics classes. Please assume it mostly correct but maybe not technically for every minute detail (the only use of "power" is technically very wrong among other things, but that's the gist of it).

Electricity is the flow of electrons, who move from negative to positive, the opposite of what you would normally expect.

Okay, so I see someone else already did an effortpost, so I'll just add on.

Benjamin Franklin assumed logically that electricity obviously must flow from positive to negative (since it’s the logical choice), but alas, he was wrong as far as history sees it.

Well, I'm sure he knew it was a guess. He was a smart man. He picked glass as the thing that picks up "electric fluid" in static electricity experiments, becoming "positively charged", in other words a positive excess of fluid, when in fact it loses electrons. Until someone invented vacuum tubes a century or so later nobody could tell the difference.

Positive-to-negative is called "conventional current", and circuit diagrams are still drawn that way. Unfortunately, the charge and direction of the particles moving (rather than just that they are moving) can become important if you want to understand electrochemistry, for example. Metal ions are positively charged (missing an electron), and so they're going to come off of the electrode where electrons being removed, and plate on to the electrode where they're being added. You have to remember the conventional current is opposite to the actual current to picture a battery running a circuit, and if it's connected to a bunch of digital chips in a complicated way, I, at least, can get lost.

If that's still unclear, any further questions are welcome.