Bluetooth Slave/Master .... what is the difference?

Hello
this is what i have read:
- Master modules and slave modules can not switch mode from each other, and only can work as a single work mode
- The master modules can only use with this slave modules, and the master modules can not match with other slave modules such as the computer?cell phones and other bluetooth device etc.
- The slave modules can match with other slave modules such as the computer?cell phones and other bluetooth device etc.
- The master modules have the same At command with the slave modules except for "AT+NAME" , which means the slave modules have At command of "AT+NAME" and The master modules don't have.

I don't understand : master modules can not match with other slave modules such as the computer?cell phones and other bluetooth device etc.

Does this mean that it cannot connect to mobile in anyway?
So when you use the Master?

I'd appreciate if someone could edecate me in this matter.

Thanks