What do the points (pts) or pounds (lbs) mean?

We indicate the thickness of card stocks by measuring them with a caliper to the nearest 1/1000" point signified by the (PT) symbol. For example a 16PT card is 16/1000" thick and a 60PT card is 60/1000" thick. The higher the point (PT) number the thicker the card stock.
Because paper is too thin too be measured with a caliper, we indicate thickness by weighing a ream of paper in it's parent sheet size, that measurement in pounds is signified by lbs. The higher the number the heavier / thicker the stock will be; for example a 100lb paper is heavier/thicker than 70lb paper.