理解 (lǐ jiě) means 'to understand' at a deeper, more empathetic level — it's used for grasping someone's feelings, reasons, or complex ideas. It goes beyond the basic 'to get it' of 懂 (dǒng) and is more intellectual than 了解 (liǎo jiě), which focuses on knowing a situation or finding out. 明白 (míng bai) is closer to 'to realize' or 'to be clear about'.