Database systems are used for a variety of use cases
Temporary hot data storage.
Long-lived cold storage.
Complex analytical operations
Access value by key
Time-series data storage
Storage large blob
There are different ways to group the databases, one of the popular way group databases into 3 categories
OLTP (Online Transaction Processing) databases: Handles a large number of user-facing requests and transactions. Queries are often short-lived.
OLAP (Online Analytical Processing) databases: Handles complex aggregations. Used for analytics queries.
HTAP (Hybrid Transactional & Analytical Processing) databases
Another way of categorization is
Document oriented stores
DBMS architecture is based on a client-server model
Nodes are server
Applications are client