Incidents are groups of related alerts that together create an actionable possible-threat that you can investigate and resolve. Azure Sentinel uses analytics to correlate alerts into incidents. Use the built-in correlation rules as-is, or use them as a starting point to build your own.
Azure Sentinel also provides machine learning rules to map your network behavior and then look for anomalies across your resources. These analytics connect the dots, by combining low fidelity alerts about different entities into potential high-fidelity security incidents.
Source: https://learn.microsoft.com/en-us/azure/sentinel/overview