What meaning is '[: , None]'?

[Robert]

Hi,

I read a code snippet, in which object w_A is:


w_A
Out[48]: array([ 0.10708809,  0.94933575,  0.8412686 ,  0.03280939,  0.59985308])


Then, I don't know what is '[:  ' below:
vs_A = w_A[:, None] * xs


I don't find the answer after searching around 
Could you explain above code to me?
Thanks,