The Articles of Confederation was the first constitution for the United States, it is known for being very weak and giving the federal government little power. Under the Articles of Confederation, the federal government could not tax the states, create and enforce laws properly, regulate trade, draft soldiers, or do other important matters.
The people who were in support of the Articles were called Anti-Federalists, many of them wanted the power to stay in the hands of the state governments, as they were afraid the federal government would abuse their power, just like Great Britain had done. The people who did not support the Articles of Confederation and were in favor of a new constitution were called Federalists, they believed that the federal government should have more power and the Articles of Confederation was weakening the country.
When the Constitutional Convention of 1787 was called, it was originally called to just amend the Articles of Confederation. This was not the case though, as the Articles ended up getting scrapped and the United States Constitution was created instead.
The United States Constitution addressed the general problem of the Articles of Confederation which was a weak federal government. Branches of government were created, including the separation of powers to keep all of the branches equal and prevent one branch from overpowering others. Checks and balances were also created to prevent the government from obtaining too much power and potentially abusing it. The federal government now had power and could things that they could not do before, like taxing citizens and properly enforcing laws. The Anti-Federalists also pushed for a Bill of Rights in order to be sure that the rights of citizens would be protected from the government.