The following contain much more information about GIMP than this chapter can provide. If you want to use GIMP for more advanced tasks, take a look.
https://www.gimp.org/ is the official home page of The GIMP. News about GIMP and related software are regularly posted on the front page.
Help provides access to the internal help system including the extensive GIMP User Manual. The package gimp-help needs to be installed. This documentation is also available online in HTML and PDF formats at https://docs.gimp.org/. Translations into many languages are available.
A collection of many interesting GIMP tutorials is maintained at https://www.gimp.org/tutorials/. It contains basic tutorials for beginners and tutorials for advanced or expert users.
Printed books about GIMP are published regularly. You will find a selection of the best ones with short annotations at http://www.gimp.org/books/.
GIMP functionality can be extended with scripts and plug-ins. Many such scripts and plug-ins are distributed in the GIMP package, but others can be downloaded from the Internet.
You can also use mailing lists or IRC channels to ask questions about GIMP. Always try to find answers in the documentation mentioned above or in mailing list archives before asking your question. The time of experienced users present on GIMP lists and channels is limited. Be polite and patient. It may take some time before your question is answered.
There are several mailing lists about GIMP. You will find them at https://www.gimp.org/discuss.html. The GIMP User list is the most appropriate place to ask user questions.
There is a whole IRC network dedicated to GIMP and GNOME desktop environment—GIMPNet. You can connect to GIMPNet with your favorite IRC client by pointing it at the irc.gimp.org server. The #gimp-users channel is the right place to ask question about using GIMP. If you want to listen to developer's discussions, join the #gimp channel.