Speed, stamina and aerodynamics are important in a time trial and triathlon bike, you want to be cutting through the air like a razor blade on wheels.
But that's not all triathlon and time trial bikes are good for, they also hold many different factors that make them stand out from the road bike. Their aerodynamic features allow them to perform optimally on the flats, giving you the edge over your competition. So while they may not be made for climbing, they will out-ride others on rolling or flat terrain.
Time Trial bikes also allow you to get into an 'aero' position more comfortably and naturally than on a road bike, and this is due to the positioning of the handlebars and the saddle. The set up gives you a more 'attacking' angle for winning times.
'Time Trial Bikes' are perfect for triathlons - hence also adopting the name 'triathlon bikes' - not just because of their speed, but because they actually help a triathlete to cycle after swimming and before running. Recent developments in bike technology have led triathlon bikes to have specific mechanics that allow more use of the rider's quadriceps, leaving the hamstrings fresh for the run leg of the triathlon!