lb is the written short form of pound or pounds when you mean weight, not money. You see it on food packets, in American cooking, and on bags at the airport: 2 lb of sugar, a 20 lb suitcase. One pound is a little less than half a kilogram (about 0.45 kg). In speech people say “pound” or “pounds”; they almost never say the letters l-b out loud, except when they are reading a label slowly. It looks as if it should come from the word pound, but it does not. It comes from libra, a Latin word for a weight and for a pair of scales. That is why the letters are lb, not pd. Though actually, the money word pound and the sign £ also go back to that same Latin libra — but on a price, £ is money, and lb is how heavy something is. In Taiwan you will meet lb on imported food and in US recipes; daily talk here uses 公斤.