A multi-line chart displays patient biomarker values over time, with each line representing a different marker and a color legend identifying them. The visualization uses D3 v5 within a React application, employing `scaleTime` and `scaleLinear` for axes, `line` with `curveBasis` for path generation, and `scaleOrdinal` with `schemeSet1` for colors. Data comes from a CSV file loaded via `d3.csv`, and hovering over a line highlights it while dimming others.