Regular tap water contains chlorine, which can be harmful to plants. Is the concentration of chlorine in tap water enough to merit setting water aside for some amount of time before using it to water my herb garden?
Can you remove it? It depends on your local water supply. Many cities across North America now use chloramine which cannot be effectively removed from the water unless you use a de-chlorinating compound, reverse osmosis or a carbon filter.
Chlorine can be removed by boiling (impractical) or leaving the water to sit so the dissolved chlorine returns to the air as a gas which is dissipated.
The issue of whether the chlorine or chlorine compounds is harmful to plants is up for debate. I can find plenty of unsupported opinions but no research papers on it. It is toxic for fish but soil chemistry is too complex and too local for me to give a definitive answer.