Question on vinyl pressings

Whats the difference between 1st pressing,2nd pressing,etc.Are there sonic differences?I have also seen first pressing sell for more.
Doesn't it just mean the first run of pressings from the stamper; and "second" would be another run from the same stamper?
Not sure but would like to know if 1st pressings sound best.I Think the mother wears out or dulls after lots of pressings.I wish some vinyl Einsteins would explain this.This thread is old and you are the only one so far to respond Carl,Thanks......
Ya welcome. Of course first pressings would have a less altered result (from wear) than a later one. That would be a more "accurate" representation of what the cutter cut.