threading in the databases

I would like to know what does it mean if some one says that a database is single threaded? And what does it mean if a database is multi threaded?

I understood it as multiple users can query a mult开发者_StackOverflow社区i threaded database and it is not possible in single threaded database.Or if there is other fundamental difference? Can some one explain?

Thanks in anticipation

It is not about how users connect to the database is about the number of operations, either to assert or query data that can be performed at the same time. Single-threaded means that only one user-operation can be run at the same time. Multi-threaded means there are multiple threads to run multiple operations at the same time and the database system has been designed in such a way that is able to control race conditions and locks between records to allow consistency according to the ACID principles.