You must wear a helmet when cycling. When people say ‘aero helmet’ they will mean either (i) a helmet with a profile similar to a classic road lid, which has been stream-lined and aero-optimised, or (ii) a ‘time-trial’ specific helmet which has a longer shape, akin to a teardrop, which is designed to fill the gap between your head, neck, and upper back when cycling in an aggressive position.
Aerodynamic helmets are helmets that minimize wind resistance. They are shaped in such a way that air flows smoothly over the head. Further, they are used for time trials and triathlons, whereby riders use them when they need to go faster with less effort. They are fast gear helmets. They are not like normal helmets because they have fewer holes and an elongated back in order to decrease air resistance. Although they trap in more heat, they provide definite speed advantage in races when air is of importance.
