What is G20 summit

Financial crisis in 1997-98, made the G7 finance ministers (USA, Japan, Germany, UK, France, Italy and Canada) to acknowledge the need of participation of major emerging market economies.
G7 finance ministers agreed to establish G20 Finance Ministers and Central Bank Governors meeting in 1999 to address the financial crisis.
The meeting focussed on major economic and monetary policy issues amongst major countries in the global financial system. It aimed at promoting cooperation toward achieving stable and sustainable global economic growth for the benefit of all countries.
The participating members in the meetings were the same as the current G20 members.
Post that, in November 2008 again faced with the global financial crisis that occurred in the wake of the collapse of the Lehman Brothers, the G20 inaugural summit was held in Washington D.C.
The G20 Meeting of Finance Ministers and Central Bank Governors was upgraded to the head of state level, as a forum for leaders from major developed and emerging market countries.
In September 2009, the third summit was held in Pittsburgh where the leaders designated the G20 as the “premier forum for international economic cooperation.”
From thereon, the summit meetings were held semiannually until 2010 and annually from 2011 onwards.