There are two main types of digital graphics: raster and vector. GIMP is intended for working with raster graphics, which are most often used for digital photographs or scanned images.
Raster Images. A raster image is a collection of pixels: Small blocks of color that create an entire image when put together. High resolution images contain a large number of pixels. Because of this, such image files can easily become quite large. It is not possible to increase the size of a raster image without losing quality.
GIMP supports most common formats of raster graphics, like JPEG, PNG, GIF, BMP, TIFF, PSD, and more.
Vector Images. Unlike raster images, vector images do not store information about individual pixels. Instead, they use geometric primitives such as points, lines, curves, and polygons. Vector images can be scaled very easily. Depending on their content, vector image files can both be very small or very large. However, their file size is usually independent of their display size.
The disadvantage of vector images is that they are not good at representing complex images with many colors such as photographs. There are many specialized applications for vector graphics, for example Inkscape. GIMP has very limited support for vector graphics. For example, GIMP can open and rasterize vector graphics in SVG format or work with vector paths.
GIMP supports only the most common color spaces:
RGB images with 8 bits per channel. This equals 24 bits per pixel in RGB images without an alpha channel (transparency). With an alpha channel, that equals 32 bits per pixel.
Grayscale images with 8 bits per pixel.
Indexed images with up to 255 colors.
Many high-end digital cameras produce image files with color depths above 8 bits per channel. If you import such an image into GIMP, you will lose some color information. GIMP also does not support a CMYK color mode for professional printing.