Why track dew point instead of relative humidity?

(WXYZ) - Don't know the difference between dew point and relative humidity?  Dew point is a much better way to track how humid the air is than relative humidity readings.  Relative humidity readings can go from very high (near 100% sometimes) in the mornings to less than 50% in the afternoon simply because the air gets warmer.  But dew point is a more constant measure of the moisture content of the air which doesn't vary as the air warms and cools.