What is a normal unit vector?

Hint: This is a pure concept-based question, as if the definition of a normal unit vector is known and the formula for it is known, then it becomes easy to write the answer for this question. Normal unit vector is also known as unit normal, which is just a terminology but the meaning of both the terms is the same.

Complete answer:
The normal vector is a vector which is perpendicular to the surface of the vector at a given point. It is also called “normal,” to a surface which is a vector. When normal’s are estimated on closed surfaces, the normal pointing towards the interior of the surface and normal pointing towards the outward are usually discovered first. The unit vector that is acquired by normalizing the normal vector is known as the unit normal vector, also known as the “unit normal”. Here, we divide a nonzero normal vector by its vector norm to obtain its value.
Vectors have both magnitude (value) and a direction. They are shown with an arrow $\vec{a}$ . $\hat{a}$ denotes a unit vector. If we want to change any vector in a unit vector, divide it by the vector’s magnitude. Usually, xyz coordinates are used to write any vector.
It can be done in two ways:
$\vec{a}=(x,y,z)$ using the brackets.
$\vec{a}=x\hat{i}+y\hat{j}+z\hat{k}$
Formula for magnitude of a vector is:
$\left| {\vec{a}} \right|=\sqrt{{{x}^{2}}+{{y}^{2}}+{{z}^{2}}}$
And the unit vector formula is:
$\text{Unit Vector = }\dfrac{Vector}{Vector's\,Magnitude}$

Note:
Terminology plays an important role in deciding the answer to the question. Now, as the normal unit vector is widely named as unit normal, both names are the same but the one mentioned in the question is basically given to confuse the student whose concepts are not clear. So, to answer this type of question it is necessary for the concept to be clear or it will become difficult to understand the terminologies used.