The repulsive interaction between the electron clouds of $\mathrm{neighbouring}$ bonds to C▬C bond on which rotation is studied, affects the stability of conformation. It is called:

Torsional strain is actually the repulsive interaction between electron clouds of carbon-hydrogen bonds. This affects the stability of the conformation. The torsional strain results mainly from the eclipsing groups. The increase in the amount of energy from the eclipsing groups of the nearby carbons is known as the torsional rise of eclipsing groups.