The only sense in which "electricity" could be said to be fluid is in its definition. There's no such physical quantity, it's just a vague term for a variety of phenomena.
As for what is flowing, my understanding is that it is electrons in an em field. which if you think about it is almost the same thing that is flowing in a molecular fluid, only that has drag a bunch of protons around at the same time limiting performance.
https://en.wikipedia.org/wiki/Hydraulic_analogy#Limits_to_th...