Databricks Runtime 7.3 LTS was a long-term supported (LTS) version of the Apache Spark environment available on Databricks. It was built on Apache Spark 3.0 and included many new features and improvements, such as:

• Easier development and debugging: Improvements to PySpark, including a new interface for Pandas UDFs.
• Improved performance and reliability: Optimizations to Delta Lake and other components.
• Enhanced security: Additional security features and controls.

However, Databricks Runtime 7.3 LTS reached its end-of-life on September 24, 2023. This means it is no longer receiving security patches or updates from Databricks.

If you are still using Databricks Runtime 7.3 LTS, it is strongly recommended to upgrade to a newer LTS version to ensure you have the latest security patches and features. You can find more information about supported Databricks Runtime versions and their end-of-life dates in the Databricks documentation or on Microsoft Learn.