A chemical conformation of an ethane-like molecule $abcX-Y$ def in which the substituents $a, b, $ and $c $ are at the greatest distance from $d , e$, and $f$ is called a staggered conformation. Explanation
Atoms/substituents connected to neighboring carbons are as widely apart as feasible in staggered conformation.
$H$ atoms on consecutive carbons have a dihedral angle $60^{\circ}\left(180^{\circ}\right.$ or $\left.300^{\circ}\right)$ in ethane, resulting in a staggered conformation.
The dihedral angle in (1) and (2) is $60^{\circ}$ degrees.
The ethane in (3) is in eclipse conformation, with a dihedral angle of $0^{\circ}$.
It is in skew conformation in (4) (dihedral angle is greater than $60^{\circ}$ ).
Thus, the configuration (1) and (2) is in staggered conformation.
