A more thorough explanation:

Edictal citation is a type of summons used in Scots and Roman Dutch law when personal service is impossible. It is treated as having been served by public proclamation. This means that if a defendant is out of Scotland or cannot be found, the court can still require them to appear by publicly announcing the summons.

For example, if someone is being sued in Scotland but they are currently living in another country, the court can use edictal citation to require them to appear in court. The summons will be publicly announced in Scotland, and the defendant will be considered to have been served.

Another example is if someone is avoiding being served with a summons. If they cannot be found, the court can use edictal citation to publicly announce the summons and require them to appear in court.