Reading Banjo Chord Diagrams
The vertical lines on a banjo chord diagram represent the 4th through the 1st strings of your banjo, moving from left to right — as if you were looking down on the fingerboard of your instrument from above. The horizontal lines are the frets on your banjo, with the top line corresponding to the banjo nut. The dark circles represent fretted positions, with left-hand fingering indicated at the bottom of the diagram.
Check out the following chord diagram for the C chord, with parts labeled.