I don't like to make too many extra assumptions on Ni, because it's a simple function and there are people who type as Percieving who are Ni dominants who may get confused at the Judging definitions of Ni. Ni and Ne are primary Perceiving functions that adhere to open possibilities. The difference is that, Ni refers to possibilities and ideas in inward perception, devoid of outward perception (Pe), while Ne refers to possibilities and ideas in the external moment and external things happening. It is outward perception. I think the foundation for this is well-described in the links in my signature as well as Lenore Thomson's book. So these are the easiest base descriptions with, I believe, no extra assumptions. Whether you're an Ni type or Ne type (in MBTI as well as Socionics) is not something you'll know from an MBTI preference test, I think it's just something you realize for yourself.
Introverted Intuition - from Personalityhacker.com and Dario Nardi
"You naturally perspective-shift to understand a problem or situation from all possible angles. People haven't spent nearly as much time as you thinking about various angles to something. You find it intrinsically rewarding to refine ideas and concepts where others don't, and because of this you are naturally insightful. When given a problem or mystery, your brain tries to harness every neocortex region together in order to “realize†an answer from different angles. Each brain region provides a different perspective, and you're able to reconcile various unusual perspectives to find a best-fit answer or strategy to a problem or puzzle. You naturally observe your own mind forming patterns, and easily get into the perspective of others. One relevant example of Ni is "There are different perspectives for categorizing people in a typology system like MBTI. People have different perspectives on their own systems and takes on the functions. Thus, for an Ni dominant, it makes it hard to get too caught up in one way over another."
Extroverted Intuition - from Personalityhacker.com and Dario Nardi
You naturally find connections between disparate things in the outside world, pushing buttons and looking for patterns. By opening up to all possibilities, you are able to create connections between people, ideas, objects, or places that discover new and unheard-of ways of thinking. You love to ask the question “What if?†and few things are as satisfying as blazing a new trail, often in both a literal and metaphoric sense. While most personality types focus in on related brain regions to answer certain questions, you naturally use trans-contextual thinking to include brain regions that seem to be unrelated to the question at hand. This helps you discover unusual relationships between situations. Most people, for instance, upon hearing the words “dog†and “cat†will evoke auditory regions and perhaps some visual or memory regions. However, you get busy trying each region at a time …for instance, you suddenly imagine a story about two brothers, one of whom is faithful and sociable (like a dog) while the other is independent and quiet (like a cat)."