whats the difference between a Module HC-05 Master and HC-06 Slave? I have a slave module (HC-06) but im not sure whats the purpose of the word "Master" in the HC-05
A slave connects to a master. A master can be a PC with a Bluetooth radio in it / plugged into USB, or it can be a "master" HC-05 module.
Note the HC-05 can work in either master or slave mode.
Examples of masters are PCs, mobile phones when using bluetooth headsets, etc.
Examples of slaves are bluetooth headsets, phones when connecting to a computer, etc.