Rather than reinventing the writer's wheel by describing the differences between internal and external conflict and how we use them in a story, let me refer you to an excellent web resource that has already done that work for me. Glen C. Strathy's "How to Write a Book Now" site may not equip you to take the literary world by storm, but he does have an excellent discussion on conflict.
As he points out, we're all familiar with the external conflicts in common plots. We know them as:
* Man vs. Man (Or to be politically correct Person vs. Person)
* Person vs. Nature
* Person vs. Society
* Person vs. Machine
* Person vs. some supernatural agency such as gods, demons, fate, etc.
We can probably rattle off a half-dozen book or movie titles to accompany each of the conflicts listed here. Often the more important conflicts, both in fiction and in our lives, are the ones that happen between our ears.
My first book, BENEATH SIERRA SKIES, pitted Robin and Brandon against the forces of nature. If survival had been their only concern, they'd have had plenty to deal with, but I also gave them the push-pull of powerful attraction vs. fear of commitment, adventure and romance both.
Think of the best novels you've ever read and you'll probably find that the conflicts are both external and internal. Enjoy this great blog on the subject.
What are the conflicts in your favorite books? Share?