The Economist has developed an excellent publication in which world debt is simply explained.
The 1st step in solving a problem is admitting you have one.
“Does it matter? After all, world governments owe the money to their own citizens, not to the Martians. But the rising total is important for two reasons. First, when debt rises faster than economic output (as it has been doing in recent years), higher government debt implies more state interference in the economy and higher taxes in the future. Second, debt must be rolled over at regular intervals. This creates a recurring popularity test for individual governments, rather as reality TV show contestants face a public phone vote every week. Fail that vote, as the Greek government did in early 2010, and the country can be plunged into imminent crisis. So the higher the global government debt total, the greater the risk of fiscal crisis, and the bigger the economic impact such crises will have.”
Please check this crucial and very simple graphic!