What do you mean by conformation and conformer (Rotamers)?

(N/A) Alkanes contain carbon-carbon sigma $(\sigma)$ bonds. The electron distribution of the sigma molecular orbital is symmetrical around the internuclear axis of the $C-C$ bond,which is not disturbed due to rotation about its axis.
This permits free rotation about the $C-C$ single bond. This rotation results in different spatial arrangements of atoms in space which can change into one another.
Such spatial arrangements of atoms that can be converted into one another by rotation around a $C-C$ single bond are called conformations,conformers,or rotamers.