Question

what is gauche butane interactions????
(don't give irrelevant answers) 

Answer 1

the term "gauche" refers to conformational isomer where two vicinal groups are seperated by a 60° torsion angle. in stereochemistry gauche interactions hinder bond rotation. sighting along the C2 - C3 bond in staggered butane, tehre are two possible relative potential energies . the two methyl groups can be in antibonding relationship or offset at sixty degree dihedral angles

Answer 2

Butane has many confirmation since its dihedrel angles get vary across C-C bonds.We focus on the central$C_2-C_3$ bond and treat the end carbon as methyl groups.Conformationally butane is more complex than ethane and propane.
In stable conformation the two methyl group lie as far  apart from each other as possible with adihedral angle of 180 degrees.This particular stagerred conformation is called anti. the other stagerred conformation has aMe-Me  dihedral angle of 60 degrees and is called Gauche. The gauche form is less stable than anti form by 0.9kcal/mol due steric hindrance between the 2 methyl groups.Such an interaction is often referred to as Gauche Butane interaction.