Translation:I have 80 cents.
毛 also means hair. Depending on the context, you can use 毛 without 钱. For example, if you were buying a stick of gum and asked the shopkeeper how much, the shopkeeper could just say, "八毛。" However, without context, people would look at you funny, because they might think you were talking about hair or feathers or something like that.
It's not a currency word, it's a measure word. Saying "yuan" means you're specifically operating with Chinese currency. Saying "kwai" and "mao" means you're operating in whatever the local monetary unit is. "Kwai" can mean "yuan", "dollar", "pound" or "peso" (or any other basic unit of money) depending on your current location
In RMB (the currency of the People's Republic of China):
The basic unit of money is the 元 yuán, informally referred to as 块 kuài.
1/10 of the 元/块 (analogous to an American dime) is the 角 jiǎo, informally referred to as 毛 máo.
1/100 of the 元/块 (analogous to the American penny) is the 分 fēn. This is rarely used, as most prices and transactions only go to the 角/毛 place.
I'm having a hard time understanding tones. 钱 has a second tone but it only sounds like a second tone when it's pronounced by itself in the voice clips. When the voice clips say it at the end of a sentence it sounds like a third or fourth tone. Is there a reason for this? Does it apply to other words with a second tone?