明白: to know something thoroughly. 了解: meaning to know about something (possibly a part of it) and have a bit of your own active thinking that shapes the a little of your own opinion.

There is no difference, by the way, there is 了解 is not 瞭解。

差不多

Almost the same meaning.

Most of the time ,明白and了解 are the same. In ancient times , 明白means knowing a thing , 了解 means knowing by heart. Now ,they both mean knowing a thing ( or a person ), or knowing by heart.