Assertion : Sigma ( σ is a strong bond, while pi (π) is a weak...

Sigma bonding involves end to end overlapping of the two atomic orbitals e.g. between $s$ and $s, s$ and $p$ and $p$ and $p$ orbitals. Pi bonding $(\pi)$ involves sidewise overlapping of the two atomic orbitals e.g. between $p$ and $p$ orbitals. Overlapping of orbitals is more effective in $\sigma$ bonding than in $\pi$-bonding. Due to the geometry of overlapping or orbitals, rotation of one atom is not
possible around $\pi$-bonds.