A colormap, or cmap, is a mapping from a range of values to a range of colors. In Matplotlib, cmaps are used to colorize data in plots. There are many built-in cmaps in Matplotlib, and you can also create your own.
To use a cmap in Matplotlib, you can use the plt.cm.get_cmap() function. This function takes a cmap name as an argument and returns a colormap object. You can then use the colormap object to colorize your data.