So what's the difference? A freeze simply means temperatures will drop to or below freezing -- which is 32 degrees. There are some types of vegetation that can be affected simply do to temperatures being too cold.
Frost is like frozen dew. When the air temperature drops to the dewpoint in the mornings, the air becomes saturated and dew develops on cars and other surfaces. When temperatures are below freezing, frost will develop instead of dew. In the morning the ground is cooler than the air above it, so if there's enough moisture present, frost can actually develop even when the air temperature is above 32 degrees. (All it takes is the surface on which frost develops to be freezing, not the air temperature).
That's why we mention that frost is likely across the Brazos Valley even though temperatures are not forecast to drop below freezing everywhere.