what is the difference between brown sugar and white sugar ?

what is the difference between brown sugar and white sugar？

White sugar is produced through a purifying process that removes a brown syrup called molasses. On the other hand, brown sugar either undergoes less processing to retain its molasses content or is produced by mixing white sugar with molasses.2019年6月7日

Simply so,Can I substitute brown sugar for white sugar?

Beside above,Which kind of sugar is healthiest?