Transition is generally the time between around 8 - 10 cms dilated, that last stretch before you are ready to start pushing the baby out. This stage generally lasts anywhere from a few minutes to and hour. Even aside from cervical checks, many women have a change in symptoms at that time.
Nausea and/or vomitting, shaking, and a general feeling of being out of control are common. Many women do find that themselves considering pain relief at that time, even if they had previously resolved not to. The good news it that this stage doesn't last too long and generally indicates that labor is almost over.
If you don't have a particularly difficult time during transition, you are fortunate. (I found it the only part of labor I couldn't manage). As long as you do not have issues with wanting to push too early from the pelvic pressure, it isn't really important that you recognize it as a distinct stage.