The GIMP is capable of reading and writing a large variety of graphics file formats. With the exception of GIMP's native XCF file type, file handling is done by plug-ins. Thus, it is relatively easy to extend GIMP to new file types when the need arises.
Not all file types are equally good for all purposes. This part of the documentation should help you understand the advantages and disadvantages of each type.
You can create new files in Gimp by using the following menuitem: -> . This opens the Create a new image dialog, where you can modify the initial width and height of the file or using the standard values. More information about this dialog can be found in Section 2.1, “New”.
A second way to create files, is to paste them as new files. This creates a new file from the image data saved in the clipboard. Detail information about this topic can be found in Section 3.9, “Paste as New”.