The Articles of Confederation was a document created so that the 13 Colonies could stand and defend themselves against British forces. It's main acomplishment was that it was the origin of the Constitution of the United States. But this wasn't without it's drawbacks though, for starters, once the war for Independence was over, the Articles didn't have much effect, and of they wanted to make any change to a law, the 13 Colonies had to sign the agreement together which was very complicated.
It's because of these defficiences that the Constitution was born and replaced the Articles of the Confederation.
Hope this helps!