regress vs polyfit

[Thomas Grzybowski]

Hi:

I am new to octave and want to fit a single regression line to some 
data.  I have been using polyfit, and was looking at regress, but I find 
regress confusing.   From the regress "Help":

 * `X' is a matrix of regressors, with the first column filled with the 
constant value 1

I do not understand the help instructions.  My data is simply x,y pairs 
- what is this help about - "the constant value 1" ?

Thanks,
Thomas Grzybowski