In the Previous basic Guitar Tuning lesson we learnd to tune guitar with Standard tuning. That is we tuned the 1st string (or last string both are tuned to same note ) with E note. You must know that you can tune guitar UPTO 2 note lower or two note higher (this is never ever preferred.). Generally is tuned lower 1 note lower that is the first thin string is tuned with D note and then other strings are tuned with the help of it. For local aur cheap guitar they are always set lower to save the freat board from the Bent effect.