The Articles of Confederation was the first constitution for the United States. Along with this, it is known for being incredibly weak and giving little power to the federal government. Under the Articles of Confederation, the federal government could not tax the states, draft soldiers, regulate trade, or even amend and create new laws.
With the Articles of Confederation being so weak, many people started to realize that having a government that actually had power would be better and strengthen the power of the country as a whole. These people were called Federalists. On the other hand, people who wanted to keep the federal government limited and keep the power in the hands of the people were called Anti-Federalists.
When the Constitutional Convention of 1787 happened, the original goal was just to simply amend the Articles of Confederation. This obviously did not happen though, as the Articles of Confederation was scrapped as a whole and the United States Constitution was created instead, which gave power to the federal government.