This is basically the large paved bus/tram station, parking lot and traffic and security vehicle thoroughfare in front of Rome's central train station.
Facing the station about a dozen or so bus stops are situated on the right side of the piazza, the parking lot is on the left. On the front left is a taxi stand. Directly in front multiple police and army vehicles parked there consistently, Italians seem to take security seriously in high pedestrian volume places.
Two metro lines (A red and B/B1 blue) also run below the piazza, stopping at Termini, from which it's possible to transfers to other forms of transportation within and without the station.
The several times I walked around or thru the square, it's never crowded, probably because there is no shade, most of the foot traffic is within the station itself. Overall pretty clean and well maintained. read more