了解 vs 明白 vs 知道 - what is the difference, and when should I use each one?
知道 means you just know something, you don't need to understand it.
了解, you understand it.
明白, you understand something, and have a clear idea of what it is about. 

I think the order of them is: 知道&lt;了解&lt;=明白

for 了解, it can also means 'to investigate'. e.g 小白, 你去了解一下这事情怎么发生的.