Conventional current in a wire flows from the positive terminal to the negative. Say for example there is a wire with an end X that has a current that flows to end Y. The charge will run from positive to negative (from X to Y). However, because the current is flowing to Y this means that end Y will be the positive end.
Conversely, for electrons, they run from the negative end of a wire to the positive end (only inside the circuit/battery). As they flow from one end of a circuit to another, the end they are flowing towards will have an excess build up of negative charges (electrons) and therfore that end will become negative, with the end they came from being positive. It is important to note that in the external circuit that the electrons will flow in the same direction as conventional current (ie. from positive to negative)
This was all very confusing to me to begin with, its lucky that my father is a physics teacher! i hope that helped out mate