The term “pesticide” is used to refer to any substance that is used to control an unwanted organism. An herbicide is a subset of pesticides that is intended to control unwanted plants, just as an insecticide is used to control unwanted insects. Another way to put it is that all herbicides are pesticides, but not all pesticides are herbicides.
That said, just because a particular substance is termed an “herbicide” does not mean that it will not or cannot have pesticidal effects upon other life forms, indeed one of the big takeaways from investigating the causes of Colony Collapse Disorder in bees has been the synergistic effect of different pesticides on bees between products used by beekeepers to, for instance, control Varroa Mite and whatever products are being used on the crop the bees are pollinating. Studies have shown that there exists the potential for a exponential increase in lethality if bees are exposed to two or more different pesticides, even if taken separately they are beneath toxic levels.
Pesticides are more rightly classified by their mode of action rather than herbicide, insecticide, fungicide, etc.
According to the professor at U Wis extension course several weeks ago there is no such data by any pesticide harming bees when used properly or in combination. His point was: THERE IS NO DATA, just anecdotal stories, beliefs and such.
However, the whole subject is highly controversial with claims made all over the place but there is no data to back up any claim - it just has not been studied in any depth and most products have never been looked at in connection with bees.
The whole herbicide/pesticide thing is just what I said but in different words.