WPF (Windows Presentation Foundation) TextBlock with gradient color allows for a visually appealing and interactive text display. It involves setting gradient brushes for the TextBlock's background to create a gradient effect. This can be done using the 'Background' property of the TextBlock and specifying a gradient brush. Gradient brushes can have different types, such as linear gradients or radial gradients, and can be customized to use various colors and opacity levels.