The pay line is literally a line extending from one side of the slot window to the other. When the wheels stop spinning, the icons under the pay line have to align in a certain order. Earlier versions of slot machines had a single pay line at the centre. But modern versions have different geometric shapes, and zigzag across the screen through the icons.  The pay table is a chart that displays how much you can win on a bet of a particular value for a certain pay line. Online slot machines have pay tables that are unique to their patterns.