They are to be discussing a lot of things. On the G20's own website (https://www.g20.org/italian-g20-presidency/priorities.html) it says "the 2021 G20, under Italian Presidency, will focus on three broad, interconnected pillars of action: People, Planet, Prosperity.
Within these pillars, we are taking the lead in ensuring a swift international response to the pandemic – able to provide equitable, worldwide access to diagnostics, therapeutics and vaccines – while building up resilience to future health-related shocks.
We are also looking beyond the crisis, towards ensuring a rapid recovery that addresses people’s needs. This implies a focus on reducing inequalities, on women’s empowerment, on the younger generations and on protecting the most vulnerable. It means promoting the creation of new jobs, social protection and food security.
The G20 is also intent on paving the way to rebuilding differently in the aftermath of the crisis. More efficiently, through a better use of renewable energies and with a firm commitment to protecting our climate and our common environment."