If you often use tools with particular settings, presets are for you. You can save these settings and get them back when you want.

Paint tools, which are normally in Toolbox, have a preset system that have been much improved with GIMP-2.8. Color tools (except Posterize and Desaturate), which are not normally in Toolbox, have their own preset system.

Four buttons at the bottom of all tools options dialogs allow you to save, restore, delete or reset presets.

Paint tool presets are described in Section 5.1, “Tool Presets Dialog”.