I included this because it is frequently asked, but the question misunderstands the importance of the scrum events. It’s like asking which of your limbs is most important. You may be able to answer, but they are really all critical.
If pressed for an answer, the daily scrum probably has the greatest impact on the team's effectiveness.
Learn more about the events in scrum. Then browse the most common terms in a Scrum glossary and learn what is Scrum.