first:the followed by two words are different. eg:you can say 我了解情况。but,you can't say:我明白情况。 second:了解 usually followed by somthing concrete,while 明白 usually followed by something abstract.eg:我了解这个人。 我明白了一个道理。 人是具体的 而 道理是抽象的。 third:了解 often used in formal ways but 明白 often used in oral speaking