CurrentWhich way does current really flow?

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Current is the flow of electrons through a conductor. It is measured in amperes (amps), A. The symbol in formulas is I, from the old word "intensity". You'll see I everywhere, for example Iₙ for a device's rating, Ib for design current, and IΔn on RCDs and RCBOs.

With no voltage, the electrons in copper just sit there vibrating. Connect a 12 V battery and they're all pushed the same way round the loop, like F1 cars off the start line. A circuit must be a complete loop for current to flow.

Conventional current: Drawn flowing positive → negative. This is the direction everyone assumes on drawings.
Electron flow: What the electrons actually do: negative → positive.
DC: Electrons flow in one direction only. Batteries are always DC.
AC: Electrons flow backwards and forwards. UK mains is AC.

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