A radar chart, also called a spider or web chart in Excel, is designed to compare different values for a single item. It consists of axes that emanate from a central point, each representing a specific metric. The axis's length indicates the value of that metric, and all the axes meet at the center of the chart. This chart type is useful for displaying multiple data points and comparing them quickly. It provides a clear visual representation of different values and can help in identifying the strengths and weaknesses of the item being compared.