The parts of lowercase letters (such as p, q or y), old style figures or some punctuation symbols going below the baseline are called descenders.

In the same typeface, all descenders need to have the same height for overall consistency.

On the opposite side, parts going above the x-height are ascenders, like in letters b, d or f.

Both ascenders and descenders don’t necessarily need to have the same length. In general, descenders are shorter than ascender