Here is are list of free graphics editors for creating and editing different types of images. Whilst some of these programs can edit photographs as well we do have a separate section for software which is specifically built for photos.
In this section you will find both raster and vector editors. If you are new to image creation and editing you will most probably want to use a raster editor ( unless you have a specific purpose in mind for which you have been told you will need a vector editor).
Some of the programs in this section are very easy to use, even for children whilst other can take a fair bit of learning. It is up to you to decide if you want to jump straight in with one of the more complicated pieces of software (if you are a good learner or have previous experience) or if you are best starting with a simpler program and working your way up.