It usually shows you've specialised in one specific area of your BSc. / BA degree - e.g. A BSc. Mathematics degree, with a MSc. Statistics. I'm not sure what an Honours degree signifies especially, although I have one and only in 3 standard years of study, not four.
If you chose a Masters degree in a subject completely unrelated to your original degree (BSc. Mathematics, MA Tap Dancing), then you'd probably need to justify to an employer (and at the Masters interview) why you have chosen to head in a completely different direction. At worst, they may think you couldn't hack it in your first choice, and are trying again, or are just fickle in your aspirations. At best, they may think you're very keen to explore entirely new areas and expand your general knowledge.
What were you planning to apply for?