When uploading a photo by using the upload button on /photos/[webname], then an (invisible) permanent link to that photo is created automatically, and that permantent link will be used by the system when embedding the photo into a post. This is very useful because the photo will always be found and shown even if you move it from one photo album to another. Another good thing is that photos uploaded like this are shown in /gallery/[webname].

Another channel [webname_two] can give you the permission to upload photos like this onto his /photos/[webname_two].