Add white Gaussian noise to signal

Any one can help me to understand how to choose the value of snr in the awgn function https://www.mathworks.com/help/comm/ref/awgn.html#fp1224540_ex3

I dont understand the real meaning of dwB and dwB stand for what ?

Thank you very much

[Raj]

Did you see here:

https://in.mathworks.com/matlabcentral/answers/40772-snr-in-awgn?s_tid=answers_rc1-1_p1_MLT

[Tran Hoa]

It is very helpful. Thank you so much