The word length indicates the number of bits you want to use in representing a fixed-point number. The integer word length specifies the number of bits, including the sign bit, you use in representing the integer part of a fixed-point number. The difference in bits between the word length and the integer word length determines the digits of precision.
The finite word length of a quantizer can affect the frequency response of the resulting fixed-point filter. The larger word length value you specify, the less the fixed-point representation distorts the frequency response. However, a larger word length value also requires more hardware resources, so you must specify a word length that provides an acceptable tradeoff between distortion and hardware resource consumption.
Use the wl and iwl inputs of the Fixed-Point Tools VIs to specify the word length and integer word length, respectively, of a quantizer.