Battery has got two leads,one positive and other negative.Electrons gather at the negative terminal of the battery and if you connect a wire across negative to positive,then the electrons from negative end will quickly flow through the wire to the positive terminal.Normally you will have a load connected in the wire which reduces the flow of electrons like a bulb or motor.
Inside the battery itself, a chemical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery’s internal resistance) controls how many electrons can flow between the terminals. Electrons flow from the battery into a wire, and must travel from the negative to the positive terminal for the chemical reaction to take place.