Why does electric current always flow from positive to negative? It is said that current flows from positive terminal to negative terminal, but it is actually the negative electrons flowing to positive as the positive electrons don't move.
The flow of electric current occurs because we have a high potential of electrons gathered at the positive terminal and a low potential of electrons at the negative terminal. It doesn't have so much to do with the charge associated with each one as it does with the fact you have an inequality between amounts of electrons available. When you complete the circuit by turning on the switch, the electrons flow naturally from the high potential to the low potential, which is from the positive pole to the negative pole. Think of it this way: if you have a stream of water, and you build a dam to hold back the water, you get a buildup, a reserve of water behind the dam. When you open the floodgate of the dam, you start a "flow" of water from the excess water you have available. This water quite readily flows to the lower levels in front of the dam, where the water levels are low. It is the same with the flow of electric current through a circuit.
The notion of flow of current from +ve to -ve is based on the concept that positive if some thing where you have something excess and negative is something which is in shortage. This is however not true in case of an electrolytic cell where +ve terminal lacks electrons and the -ve terminal has excess electrons. Actual situation is described below:
Inside a electrolytic or galvanic cell the electrons flow from the Carbon Rod (anode) to the Zinc Shell (cathode) and by virtue of that there is shortage of electrons on the anode and it gets a positive charge. On the other hand, electrons accumulate on the cathode and it gets the negative charge. When anode and cathode of the cell are connected by a wire through a lamp, the electrons (current) actually flows through the circuit from cathode (-ve terminal) to anode (+ve terminal) in the wire and lamp and from +ve to negative in the electrolite.
You can see from the above example the actual status of current flow but it has been made a convention to say that the current flows from +ve to -ve terminal. However the factual position is otherwise.
The actual flow of negatively charged electrons is from cathode or "-ve" pole to the anode or "+ve" pole and that notation of current flow is named "Electron flow".
However the discovery of the actual charges of electrons came much later than the discovery of electricity. Before that, it was conventionally considered that current flows from +ve pole to -ve pole. That notation of flow of electric current was named "Conventional current flow" which is opposite to that of "Electron flow" or actual flow of charges.
Since then, basic laws of electric circuits "Ohm’s Law and Kirchhoff’s Laws" remain just as valid with either style of notation. Most textbooks and electrical engineers kept using the conventional current in their calculations since that would not affect the final outcome.