Imagine the pop songs of American Idol crossed with the national fervor of the Olympic Games. That's the Eurovision Song Contest, which takes place this week in Lisbon, Portugal. This is the 63rd annual Eurovision, and it's being held in Lisbon because last year's winning song was the Portuguese entry, "Amar Pelos Dois," sung by Salvador Sobral.

Each participating nation sends one song to be performed in a live TV concert that is broadcast to all the competing nations. Most of the entrants are the member nations of the European Broadcasting Union, though a few other countries have participated. Despite the "Euro" in "Eurovision," not all of the competing nations are European. Israel and Cyprus are regular entrants, and Morocco took part once. Australia was invited as a special guest for the 60th anniversary contest in 2015; what was intended as a one-off has become a permanent invitation, and Australia is now a regular competitor. The competition is broadcast in several countries that aren't participants; in the United States the finals have been aired for the last few years on the Bravo cable network.

Forty-three nations are taking part in this year's Eurovision, the most entrants ever. (This compilation includes all 43 of this year's songs.) For several years now, the number of entrants has been large enough that semi-finals are required to narrow the field before the finals on Saturday, May 12. The so-called "Big Five" nations – France, Germany, Italy, Spain, and the United Kingdom – automatically qualify for the finals, as does the host country. The other 37 entrants will take part in two semi-finals on Tuesday, May 8 and Thursday, May 10, with ten songs from each semi-final being voted through to join Portugal and the Big Five in Saturday's finals.

Each nation casts two sets of votes – one from a 5-member jury of music professionals, and one from the public by telephone vote after all of the performances have concluded. Each set of votes awards 12 points for 1st and 10 points for 2nd, with 3rd through 10th counting down from 8 points to 1. No country is allowed to vote for its own entrant.

A few Eurovision winners have used their victory as the springboard for a successful career, most famously ABBA, who won the 1974 competition with "Waterloo." Céline Dion won in 1988 with "Ne partez pas sans moi," representing Switzerland (the rules don't require singers to be from the country they represent). 1976's "Save Your Kisses for Me" was a small hit in the United States for Brotherhood of Man. And while they never caught on in the US, the 1981 winner, "Making Your Mind Up," started a long run of hits in Europe for Bucks Fizz.

Some winners were already famous when they won the contest. Sandie Shaw had landed several hits in England when she won the 1967 Eurovision with "Puppet on a String;'" Lulu was at the peak of her career when "Boom Bang-a-Bang" won in 1969; and Katrina and the Waves had a comeback in 1997 with their winner, "Love Shine a Light." Lulu's 1969 win was part of a 4-way tie for first; an elaborate system of tie-breakers is now in place so that there will never be another tie.

Ireland has been the most successful country at Eurovision, winning seven times. Among them is the only singer to win the contest twice, Johnny Logan, who won in 1980 with "What's Another Year" and in 1987 with "Hold Me Now." Logan also wrote Ireland's 1992 winning song, "Why Me?," sung by Linda Martin.

Eurovision winners tend to be bright, chipper pop songs, frequently with nonsense refrains -- for instance, 1968's "La, la, la" from Spain's Massiel; 1975's "Ding-a-Dong," from The Netherlands' Teach In; or 1984's "Diggi-Loo Diggi-Ley," from Sweden's Herreys – or sentimental ballads like Sobral's winner from last year. There is an occasional exception; Finnish metal rocker Lordi won in 2006 with "Hard Rock Hallelujah."

The rules have changed several times about whether contestants are required to sing in the language of their country. Since 1999, entrants have been allowed to since in whatever language they choose, and most of the winners since then have been in English.

In addition to the songs linked above, the following Eurovision winners are available for streaming at either Hoopla or Freegal:

• 2014: "Rise Like a Phoenix," Conchita Wurst, Austria

• 2012: "Euphoria," Loreen, Sweden

• 2010: "Satellite," Lena, Germany

• 2009: "Fairytale," Alexander Rybak, Norway

• 2005: "My Number One," Helena Paparizou, Greece

• 2004: "Wild Dances," Ruslana, Ukraine

• 1995: "Nocturne," Secret Garden, Norway

• 1994: "Rock 'n' Roll Kids," Paul Harrington & Charlie McGettigan, Ireland

• 1993: "In Your Eyes," Niamh Kavanagh, Ireland

• 1990: "Insieme: 1992," Toto Cutugno, Italy

• 1982: "Ein Bisschen Frieden," Nicole, Germany

• 1973: "Tu te reconnaitras," Anne-Marie David, Luxembourg

• 1971: "Un banc, un arbre, une rue," Severine, Monaco

• 1966: "Merci, Cherie," Udo Jurgens, Austria

• 1965: "Poupee de cire, poupee de son," France Gall, Luxembourg

• 1964: "Non ho l'eta," Gigliola Cinquetti, Italy

• 1962: "Un premier amour," Isabelle Aubret, France

• 1961: "Nous les amoureux," Jean-Claude Pascal, Luxembourg

• 1960: "Tom Pillibi," Jacqueline Boyer, France

• 1959: "Een beetje," Teddy Scholten, The Netherlands

• 1958: "Dors, mon amour," André Claveau, France

• 1957: "Net als toen," Corry Brokken, The Netherlands

• 1956: "Refrain," Lys Assia, Switzerland