The principle of completeness type:
No operation should be arbitrarily limited to the types of values involved. - watt
First-class values can be evaluated, passed as arguments, and used as composite values of compound values. Functional languages try to make no distinction in a class, while imperative languages usually treat functions (if better) as values of the second class.
Almost all programming languages limit the types of objects that can pass as values (and, therefore, have a significant type). In C or C ++, functions are not values, although pointers to functions. Classes are not values.
In Java, methods and classes are not values, although you can get a reified object representing the class as a value, and in Java 8, you can pass method references as values. Packages are not important.
In Haskell, functions are first-class values, so they can be passed as arguments and returned as values. Because Haskell is statically typed, the type system is able to express function types.