Most people regard a Triathlon as a race of 3 disciplines; swim, bike and run. However the transition is often referred to as the ‘4th discipline' and it too requires consideration and focus as a poor transition can be costly in terms of time, energy and your positivity.
A Triathlon will have two transitions:
T1 is from Swim to Bike
T2 is from Bike to Run
Each of these is very different in their requirements but is very similar in the way that they should be approached.