These actually have fairly technical definitions when you get further in statistics, but a, I guess, easier to process version of them are when you have a left tail, you tend to be, when you are left-tailed, you also tend to be skewed to the left. And when you are right-tailed, you tend to be skewed to the right. Another way to think about skewed to the left is that your mean is to the left of your median in mode. That might not make any sense to you. You might just want to go after the tail. If you're left-tailed, you're probably left-skewed. If you're right-tailed, you're probably right-skewed.