Rugby World Cup 2015 kicked off with England, the home nation, hosting Fiji at the storied Twickenham Stadium in London, the largest venue in the world dedicated solely to rugby union; the 82,000 capacity stadium has come some way since the Rugby Football Union in 1907 bought a 10 ¼-acre market garden that was used to grow cabbages, and the Rugby World Cup has developed similarly since it was first staged in New Zealand in 1987.

The Rugby World Cup now is a money-making machine, one of the biggest events on the global sporting calendar after the Olympic Games and soccer's world cup, and it seems unbelievable to think the Home Unions of England, Scotland, Wales and Ireland were not in agreement when the tournament was first proposed; the tournament was staged only after the votes of England and Wales were split, as Scotland and Ireland adopted an "over my dead body approach", and New Zealand, the ubiquitous world No.1 rugby team, fittingly, won the first final on home soil against France.

Enough of the history lesson.

How does the tournament work?

The finals feature 20 qualifiers grouped into four pools of five from which the top two teams in each group reach the knockout stage - the play-offs if you will. We then have sudden-death quarterfinals and semifinals before the finale to decide the world champions. Certainly more simple than the Laws of the Game. Here's the Rugby World Cup fixture list to illustrate who plays whom, where and when.

Who qualifies?

Twelve teams qualified by virtue of the performance in the previous tournament, in New Zealand, again, in 2011, when New Zealand, again, won the grand final against France, again, in Auckland, again. The other eight teams qualified through regional competition. Only Russia of the 20 teams that competed in 2011 is absent this time - the Bears replaced in the draw by Uruguay.

Chris Robshaw© Photo by Michael Steele/Getty Images

How are the pools decided?

Good question, one many have asked since the 2015 groups were announced in December 2012 - nearly three years ahead of the tournament. The seedings were based on the teams' respective world rankings at the time with the 12 automatic qualifiers from 2011 allocated to one of three bands based on their rankings. The remaining eight qualifiers were allocated according previous World Cup. The vagaries of the rankings at the time meant we had a "Pool of Death" often seen at soccer's equivalent tournamant but never seen before in rugby; this time we have Australia, England and Wales, all potential finalists, drawn alongside heavy-hitting Fiji in Pool A. You can be sure World Rugby, the governing body, will move to ensure such a scenario does not shake out again in the future.

Who's won before?

England 2015 is the eighth Rugby World Cup. New Zealand, South Africa and Australia have each won twice, with England the only champions from the northern hemishphere.

Who's going to win in 2015?

Another good question. Perhaps the only question that matters.

New Zealand are undoubtedly the best team in the tournament, and they are short-priced favourites to become the first three-time champions. But they have an unenviable record of failing to deliver outside their home land - "chokers" is the label they have been handed - and this tournament is considered to be the most open in history. New Zealand, England, Australia, South Africa, France and Ireland are all considered potential champions. ESPN's rugby reporters have delivered their fearless predictions for the tournament, including their thoughts about the likely champions.