Electrochemical cells can be made from 2 different metals dipped in salt solutions of their own ions and connected by a wire. Electrons flow due to oxidation on one electrode and reduction in another electrode. The electrode the electrons flow to is the positive electrode and the electrode the electrons flow from is the negative electrode.
When drawing the conventional representation of cells, it is important to draw the more negative elctrode potential on the left and the less negative on the right. The left one being the half cell that is oxidised (i.e. lost electrons to the positive electrode).
Commercial applicaions of electrochemical cells include lithium ion batteries, rechargeable cells as well as a more environmentally-friendly hydrogen-oxygen fuel cell.