Normal Plane
The normal plane is a plane that contains the principal, normal, and binormal vectors. It is an important concept in the study of curves and surfaces in three-dimensional space.

Principal, Normal, and Binormal Vectors
Before we understand the normal plane, let's first define the principal, normal, and binormal vectors:

- Principal Vector: In the context of curves, the principal vector represents the direction of the curve at a given point. It is tangent to the curve and points in the direction of increasing parameter value.

- Normal Vector: The normal vector to a curve at a point is perpendicular to the tangent vector at that point. It represents the direction in which the curve is bending or curving.

- Binormal Vector: The binormal vector is perpendicular to both the tangent vector and the normal vector. It completes the orthogonal set of vectors.

The Normal Plane
The normal plane is a plane that contains all three vectors: the principal, normal, and binormal vectors. It is defined as the plane that is perpendicular to the tangent vector at a given point on the curve.

The normal plane provides important geometric information about the curvature and torsion of the curve. It helps us understand how the curve is bending and twisting in three-dimensional space.

Application of the Normal Plane
The normal plane is used in various applications, including:
- Calculating the curvature and torsion of a curve
- Understanding the local geometry of a curve
- Constructing surfaces that are tangent to a given curve at a specific point
- Analyzing the behavior of a curve in different directions

Conclusion
In summary, the plane that contains the principal, normal, and binormal vectors is called the normal plane. It is an important concept in the study of curves and surfaces in three-dimensional space. The normal plane provides valuable geometric information about the curvature and torsion of a curve and is used in various applications in mathematics and physics.