Flot.tooltip is a jQuery plugin that adds interactive tooltips to charts created with the Flot plotting library. It enhances Flot charts by displaying informative tooltips when hovering over data points, supporting various chart types including time series, pie charts, and stacked graphs. The plugin offers extensive customization options for tooltip content, formatting, and appearance, making it ideal for developers who want to provide detailed data insights in their Flot-based visualizations.