On a wine pairing chart, markers such as colored diamonds or circles indicate where specific wines and foods intersect. These markers suggest the two items taste well when paired.
Wine charts are usually constructed as grids. Some charts are more complex than others and display a wider variety of wine and food, but the system for most grids is the same.
A good example of a simple wine pairing chart is located on WineIntro.com. Across the top of the chart is a list of six types of white wine, each in its own column. Along the side of the chart is a list of 16 types of food, each in its own row. Each row intersects with each column, with diamond markers positioned in some intersections but not others. The intersections that feature diamond markers indicate that the corresponding items work well as a culinary pairing. For example, this chart suggests that oysters go well with Chardonnay or Sauvignon Blanc.
The chart shown on WineFolly.com works according to the same system, but features many more options for food and wine. The Wine Folly chart includes a Venn diagram to help users pair wines with meals containing multiple types of food.