听

Why does 听 look like this?

The character consists of 口 (kǒu - mouth) on the left and 斤 (jīn - an axe/weight) on the right. While the modern form is simplified, you can think of it as using your 'mouth' to respond to what you 'hear' through your ears! The right side '斤' originally acted as a phonetic hint in the traditional version (聽).