Hello,
PVT stands for Process voltage and tempreture variation
Process means that the transistor ,resistors or capacitor or any other circuit element may be fabricared is typical ,fasr or slow modes.
let me give you an example if you concern digital circuits :
fast corners means min capacitance and resistance so give min delay and best speed performance.
while slow corners means max capacitance and resistance so give you max delay and worst speed performance.
voltage variation usually concern your circuit supply varition.
how much this supply vary this will reflect your circuit performance.
for example:
for supply 1.2 vary between 1.1 and 1.3
in 1.1 case it may reflect the output swing for example.
for tempreature,
typical temp usually mean roon tempreature 27 deg
tempreature variation that usually reported in data sheets nowdays between -40 and 85
Best Regards,