Here is a model of staggard ethane.Yellow ball represent the C atom and green ball represent the H atom.

In the staggered conformation, all of the C-H bonds on the front carbon are positioned at adihedral angle of 60° relative to the C-H bonds on the back carbon.

The distance between the bonds is maximizedanddecreases the electrostatic repulsion between the electrons and results in a more stable structure.