It's nothing, it's matter of convention. if you start work with electrochemistry you could find both current direction, additionaly there are different signs of the same ions - for instance oxygen ions (O2-) could be treated as negative or positive!!! depends on effect you would like to explain. So don't be supprised.
The engineering area has been using positive flow since Ben Franklin made the first polarity error 250 years ago or so. Physics also uses the positive version.
The electron flow description only is used in training military technicians and hobbyist because it is easier to visualize electron flow in metal.
man i hate ben franklin!!! honest this is the only and the hardest part of learning EE! Unfornatualy I took physics before basics electronics course at my school. I learned to calculate electrons speed, moment ect (electron as particle instead of wave) and got the image of an electron stuck in my head where should the electron go. So I always imagine electron flows opposite direction of ben franklin's style.... but then the textbook confused the crap of out me. I mixed match styles and confused myself even more. The thing ONLY one needs to remember is that any charge going around and come back to the same position (potential) has done no work... otherwise you could create infinite energy and break the energy conservation law. that helps me overcome ben franklin's purposely confusing all new ee students (maybe he intended to confuse everyone)
so basically voltages sum up around the whole path from a same start and end node should must zero. current into branches should be equal out of branches (otherwises some charges dis/appear to/from black hole?)