The Articles of Confederation were just a beginning outline of what the Constitution did.
The articles of Confederation had 2 omissions that the Constitution added.
1. There was no executive branch to enforce the laws
2. There was no judicial branch to interpret the law.
3. The Federal government couldn't collect taxes. They got their money from the states.
4. The Feds couldn't issue a standard currency. Each state had it's own.
5. Trade was not uniformly practiced by the states.
6. Often the states wouldn't pay the Federal Government because they feared other states wouldn't pay either.
7. The Constitution introduced a supremacy law where the laws of the Federal Government were above state law.
There were a couple of minor fixes
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8. Laws governing commerce between the states was introduced into the constitution
9. The federal government determined how trade was to be conducted between the states and other sovereign nations.