Are there any major differences between North Korean and South Korean? Is there anything that tends to cause difficulty communicating or are there just more minor issues (like accents or idioms)?
This was one of our definition questions.
I think the dialect tag is a good one to put here as it basically summarizes the idea of the differences here: enough to be like two separate dialects (simplifying, Korean has 9 dialects). To my understanding Korean spoken in the North has aimed to be 'pure' in a sense - that is refraining from having loan words from the Japanese language (English too, really just most borrowed words) like Korean in the South does. There are too many differences to list as a full answer, but here are a few more differences:
As a born and raised in South Korea. The difference between South and North are.. (imo)
these sites list some vocab differences like doughnut and sandwich