Explanation:

The pi-bond involves side-wise overlapping.

Overlapping of Atomic Orbitals:
When two atoms come close to each other to form a covalent bond, their atomic orbitals overlap with each other. The overlapping of atomic orbitals results in the formation of molecular orbitals.

Sigma Bond and Pi Bond:
There are two types of covalent bonds: sigma (σ) bond and pi (π) bond. The sigma bond is formed by the overlapping of atomic orbitals along the internuclear axis, whereas the pi bond is formed by the side-wise overlapping of atomic orbitals.

Formation of Pi Bond:
The pi bond is formed by the overlap of two p-orbitals that are parallel to each other. The p-orbitals have a dumbbell shape, with a node at the nucleus and a high electron density on either side of the nucleus. When two p-orbitals approach each other, their electron clouds overlap sideways, resulting in the formation of a pi bond.

Side-wise Overlapping:
Side-wise overlapping is also known as lateral or parallel overlapping. In this type of overlapping, the p-orbitals overlap sideways, with their electron clouds aligned parallel to each other. This type of overlapping allows for the formation of pi bonds.

Characteristics of Pi Bond:
- The pi bond is weaker than the sigma bond.
- The pi bond is formed by the overlap of two p-orbitals.
- The pi bond is restricted to double and triple bonds.
- The pi bond is formed above and below the internuclear axis.
- The pi bond is responsible for the rigidity and stability of double and triple bonds.

Therefore, the correct answer is option 'B' - side-wise overlapping.