If you mean the difference between 其他 and 别的。 别的is generally used when referring to something in the same 'group', whereas 其他 can refer to things outside that group. So you could say I don't want to drink Green Tea, I want to drink 别的。 So in this case 别的 refers to a different type of tea. If you say 我要其它的。 It could be anything, a coffee, a croissant, it doesn't have to be in that group.
The same goes for people 别的人 refers to people you have a connection with. If you went into an office where you didn't know the people, it would be odd to use 别的人 or 别人,if you wanted to know where the other people in the office were, you would use 其他。
We kind of do that in English a bit. So for example, 'where are the others?', it kind of implies a relationship.
I think there may be a rule for numbers as in when saying 'another' number. Perhaps you can only say 其他 for digits, but see if a native speaker can confirm that!