A NoSQL key-value store inside an Azure Storage account. Each entity is identified by PartitionKey and RowKey and can have different properties, with no fixed schema. It doesn't support joins or foreign keys.
In DP-900 it is the low-cost option for simple key-value entities. If you need global distribution or guaranteed latency, Azure Cosmos DB for Table is compatible with the same API.
Azure Table storage is a concept that can show up on the exam. Check the full guide to see it in context.