A left-skewed distribution has a long left tail. This is also called negatively-skewed distributions. That’s for the reason that there is a long tail in the negative direction on the number line. The average is also to the left of the peak.
A right-skewed distribution has a long right tail, or positive-skew distributions. That’s for the reason that there is a long tail in the positive way on the number line. The average is also to the right of the peak.