PVT stands for Position, Velocity and Time.
In real time a GNSS receiver can derive a PVT solution once it has measurements based on the pseudoranges and pseudorange rates of at least 4 SV's from the same GNSS.
In the simplest case this derived solution is only an estimate of PVT. This is because the pseudorange and pseudorange rates provided by the GNSS receiver are noisy and biased measurements of user-satellite ranges and range rates respectively.