An image is a link to an image file that does not have a description part, for example
./img/cat.jpg
If you wish to define a caption for the image and maybe a label for internal cross references (see Hyperlinks), make sure that the link is on a line by itself and precede it with ‘CAPTION’ and ‘NAME’ keywords as follows:
#+CAPTION: This is the caption for the next figure link (or table) #+NAME: fig:SED-HR4049 [[./img/a.jpg]]