What is Azure SQL Hyperscale and when you can benefit from it?

Azure SQL Hyperscale was introduced in September 2018, however, still is not used very often. What is Azure SQL Hyperscale? Is it still a relation database engine? What are the architectural differences compared to Azure SQL Database? Is Azure SQL Hyperscale is going to replace Azure Synapse Analytics (former Azure SQL Data Warehouse)?
On the session, there will be the answers to all these questions.