"mysqld" is MySQL server daemon program which runs quietly in background on your computer system. Invoking "mysqld" will start the MySQL server on your system. Terminating "mysqld" will shutdown the MySQL server. Here is a tutorial example of invoking "mysqld" with the "--console" option:

>cd mysqlin

>mysqld --console

... 21:52:54 InnoDB: Started; log sequence number 0 43655

... 21:52:54 [Note] mysqld: ready for connections.

Version: '5.0.24-community' socket: '' port: 3306

MySQL Community Edition (GPL)

The returning message indicates that "mysqld" running now, and your MySQL server is ready to take client connections. To know about "mysqld", read other parts of this FAQ collection.