*What* is a "Trans Woman"?
It's a common way of identifying that more recent generations use. Trans indicates they are transgender or uncomfortable with their birth gender. Woman is how they identify and their end goal. Some use it after they have completed their transition to indicate their path in life.
Transsexual was common when I transitioned though the term transgender was known. After we completed our transition, we would use transsexual in the past tense to indicate our path in life.
When I reentered the community after being absent from it for over 30 years, I found a number of things had changed and there was a new language to learn. Clocking meant being read, transgender was common and transsexual was rarely use and terms like GG for genetic girl had been replaced with CIS woman.
It made me feel a little like Rip Van Winkle waking up after a long sleep to discover the world had gone through many changes. What really drove the point home was when I first started giving advice, I explained that there would be 6 days of bed rest after surgery. Everybody responded that it would only be two days. Somewhere in my absence, the doctors decided it was better to get you back on your feet as soon as possible so 4 days of bed rest vanished. From that point on, I was more careful about things I hadn't verified and I updated myself on current treatment standards.