You see the term "180 gram!" bandied about by audiophiles. Beside the premium collectors double LP edition are the words "180 G Audiophile Vinyl" or perhaps 120, 150 and even 200 gram vinyl. But what does this mean really? Is a radioman even the right person to ask? Well no, the fidelity of radio is pretty much crap due to the compressed dynamic range but that's beside the point. Here are the basics:
120-140 gram is "normal." Today this is standard for any commercial pressing. If it fails to specify this is the likely range.
140 - 160 grams vinyl is the middle ground. That said, the middle ground is largely unoccupied. Vinyl tends to be either cheap or marketed to audiophiles. This range will usually be older pressings from the 1960s and some contemporary European pressings.
180- 200 gram is the holy grail in vinyl. When a classic record is repressed and re-released this is often the format. This is what they market to those big-spending audiophiles.
The basic measurement behind those grams is thickness. The diameter obviously is standardized. The thickness is not. So the idea is that a thicker record is less prone to warping. There are also less credible claims to auditory improvement. It's been said to be less noisy which really has more to do with the grade of vinyl. But there is some substance to the claim of better bass response. A deeper record groove is able to record a lower tone. This has certain limits due to the standardized record needles and response limits of stereo systems and that old standard we call human hearing. (An old engineer once told me about a prog-rock band that put out a record that was half an inch thick anyone remember this?)
As I often say.. just clean your records, treat them well and they will sound fine. Vinyl grading is mostly bogus.