A multi-line chart displays multiple frequency-domain signals stacked vertically, each with its own amplitude trace and label. The visualization uses D3 v4 to render the data as animated SVG paths, with a skewed perspective and brush-based zooming for interactive exploration. It leverages `d3.scaleLinear`, `d3.axisBottom`, `d3.brushX`, and `d3.line` to handle scaling, axes, brushing, and path generation, while the data comes from a JSON array containing signal measurements.