A bond between two carbon atoms is formed by the overlap of  $\text{s}{\text{p}}^3$  hybrid orbitals of carbon atoms along their internuclear axis as a result of which the electron distribution within the molecular orbital thus formed is cylindrically symmetrical along the internuclear axis. Due to this symmetry, rotation about carbon-carbon single bond is free, as a result number of momentary arrangements of atoms called conformations or rotational isomers.

Example: The two conformation of ethane are possible.

Conformers can be interconverted through rotation about $\text{C-}\text{C}$ bond.