What is the difference between pressure forming and vacuum forming in plastic tray manufacturing?

Question

What is the difference between pressure forming and vacuum forming in plastic tray manufacturing?

Answer 1

vacuum forming is used to form more complicated parts like refrigerators lining, but pressure forming is used when less complicated part is in need.

Answer 2

when I made plastic parts for GM, the pressure forming would blow in the plastic pellets and the parts would form under high pressure of hot air. and the vacuum would suck the pellets into the machines dye and form after of course being heated to melting temps.