For Deskdiary:
A country is automatically eligible for entry into the Eurovision Song Contest if it has one or more broadcasters that hold full membership of the European Broadcasting Union. That includes countries from outside the geographical boundaries of Europe, such as Cyprus, Algeria, Azerbaijan, Israel, Jordan, Egypt, Tunisia and Lebanon. Most eligible countries opt to take part but some don't. Also, Liechtenstein, for example is in Europe but not an EBU member, so it can't participate.
Other countries have broadcasters that are associate members of the EBU, such as Australia, Japan, India, Mexico, the USA and Canada. The competition is particularly popular in Australia, so it was decided to invite the country to compete, for one year only, on the 60th anniversary of the contest in 2015. The plan was that, unless Australia won that year, they wouldn't be invited to participate again but so many people enjoyed having Australia take part that it was decided to continue to inviting them indefinitely.