How different wavelets create different approximation sub-band?

Hello,I am using wavelet toolbox for feature extraction from images. I use 1 level wavelet decomposition.Now my question is that why and how different wavelets create different sub-bands. for example why approximation sub-band in bior3.5 is different from haar or sym20?and what is the effect of wavelet order (N) or vanishing moments on approximation sub-band?