If the link does not look like a URL, it is considered to be internal in the
current file. The most important case is a link like
‘[[#my-custom-id]]’ which will link to the entry with the
CUSTOM_ID property ‘my-custom-id’.
Links such as ‘[[My Target]]’ or ‘[[My Target][Find my target]]’ lead to a text search in the current file for the corresponding target which looks like ‘<<My Target>>’.
Internal links will be used to reference their destination, through links or numbers, when possible.