Gnuplot is a free and open-source software tool for creating and displaying plots and graphs. It supports a wide variety of output formats, including PDF, PNG, and SVG. Gnuplot can read data from a variety of sources, including text files and databases, and it offers a range of plot types, including 2D and 3D plots, histograms, and heatmaps. The software is highly customizable, with a wide range of options for controlling plot appearance and behavior.