What exactly is the Duckworth-Lewis method?

What exactly is the Duckworth-Lewis method?

Two statisticians, Frank Duckworth and Tony Lewis devised the Duckworth-Lewis method and was first implemented in second ODI between Zimbabwe and England the year 1996/7. It is a method to calculate the target score for the team batting second in a one-day cricket match interrupted by weather or other circumstance. It is a rule which is equally hated and loved by fans and preferences change according to situation. It has played a key role in deciding the fates of some big teams like South African at the World Cup.
The essence of the D/L method is "resources". Each team is taken to have two "resources" to use to make as many runs as possible: the number of overs they have to receive; and the number of wickets they have in hand. At any point in any innings, a team's ability to score more runs depends on the combination of these two resources. Looking at historical scores, there is a very close correspondence between the availability of these resources and a team's final score, a pattern which D/L exploits.
Though this method is internationally accepted, some feel that it does not take into account, the actual scenario in which the match has progressed until it stopped. But as they say, a rule is a rule.