What are the differences between value type and reference type in programming languages?

Value types (for example, struct, enum, primitive numeric types) store their value directly. When assigned or passed to a function, a copy of the value is created. Reference types (for example, class, function, closure) store a reference to the memory location where the actual value resides. When assigned or passed, a copy of the reference is created, pointing to the same value in memory.

Main differences:

Characteristic	Value Type	Reference Type
Storage method	The value is stored directly in the variable	The variable stores a reference to the value
Assignment	Copies the value	Copies the reference (points to the same object)
Modification	Changing the copy does not affect the original	Changes via the reference affect the original
Memory location	Usually stack (for local variables)	Usually heap
Memory management	Automatic (when leaving scope)	ARC (Automatic Reference Counting)

Example in Swift:

// value type
struct PointStruct {
    var x: Int
    var y: Int
}

var point1 = PointStruct(x: 1, y: 2)
var point2 = point1 // copies the value
point2.x = 10

print(point1.x) // outputs 1
print(point2.x) // outputs 10

// reference type
class PointClass {
    var x: Int
    var y: Int

    init(x: Int, y: Int) {
        self.x = x
        self.y = y
    }
}

var point3 = PointClass(x: 1, y: 2)
var point4 = point3 // copies the reference
point4.x = 10

print(point3.x) // outputs 10 (the object changed via the reference)
print(point4.x) // outputs 10