Strictness of syntax and language. It means that ctrl+space gives you exactly right methods into popup, that if you rename the class all places that use that class and no other will be changed, you can rename method and trust that all correct calls will be renamed too and no other.

You can find all the places that call a method and know they are really all. That sort of basic thing.

E.g. not for writing, but for analyzing what unknown code does and for refactoring that code. Comparing to javascript, in js you have to be much more careful when refactoring and changing things.