Hello everyone,
I am a new guy in the Arduino family and I really want to learn and do many projects with this "system" 
I stumbled across the Arduino MiniUSB and read the very incomplete description
Can somebody provide more complete one?
(For example what are these and what they do:
DCD,CTS,DSR,RI,RTS,DTR,..... :-?)
Welcome to Arduino!
It would seem that those pins correspond to pins on the FT232RL chip onboard.
For more information about what those pins do, I would consult the FT232RL datasheet.
Okey can anyone provide more help than this? 
DCD,CTS,DSR,RI,RTS,DTR are all acronyms.
Data Carrier Detect,
Clear To Send
Data Set Ready
Ring Indicator
Ready To Send
Data Terminal Ready
Once upon a time they were important for controlling serial-based communications. For instance, a modem would pull up (provide a signal) on RI to show that it was being called.
Similarly, things like DSR would be signalled to indicate that some piece of equipment was available.
Unless you're intending to use the signals, you probably don't need to know. The USB host uses software (on Windows, a serial port emulation driver) to allow independent control of these lines through a familar API, and the FTDI chip decodes the information to pull up or down the individual lines.
I've used Arduino for a while, and never needed to know anything about this (although I already did)
Try looking here:-