Combining it all :
ln -s arg1 arg2 => creates a symbolic link
if both arg1 & arg2 are file names, agr2 becomes a link and points to file arg1
ln -s file1 file2 => file2 is now a link name that points to file1.
ln -s file2 file3 => ambiguity -> file2 is the name for a link as well as a file, link is prioritized over file so file2 is no more a filename. file3 becomes a link pointing to link file2(pointer to another pointer)
Hence all point to file1 & data of file2 & file3 are lost.