How to draw one
Pick the C–C bond you want to look down. The front carbon's three substituents form a "Y" — three lines spaced 120° apart, meeting at a point. The back carbon is a circle behind the Y, with three lines coming off the circle, spaced 120° apart. The rotational angle (dihedral) between the front "Y" and the back lines is what we vary.
Staggered conformations
When back lines bisect the angles of the front Y (60° offset), you have a staggered conformation. If the two largest groups are 180° apart, it's anti-staggered — usually the lowest energy. If they're 60° apart, it's gauche-staggered — slightly higher because the big groups are crowded together.
Eclipsed conformations
When the back lines hide behind the front lines (drawn slightly offset for visibility), it's eclipsed. Two H-H eclipsings cost ~4 kJ/mol each; H-CH₃ costs ~6 kJ/mol; CH₃-CH₃ costs ~11 kJ/mol. The full eclipsed conformation of butane (with two methyls overlapping) is the highest-energy point on the rotation curve.
When this matters
Newman projections explain why butane spends most of its time in the anti conformation, why ring substituents have preferred positions, and why some reactions need specific stereochemistry — like the anti-periplanar requirement for E2 elimination, which becomes obvious the second you look at the Newman down the breaking bond.
Draw this on the whiteboard
Open the OChem Board whiteboard — benzene rings, wedge/dash bonds, and a clickable periodic table built in. No account needed.