Value types:

• Stored on the stack.
• Directly contain their data.
• Assignments create copies.

Example:

int x = 10;
int y = x; // y gets a copy of x's value
x = 20; // y remains 10

Reference types: 

Store a reference (memory address) to the data on the heap. Examples include string, class, and arrays. Assigning a reference type copies the reference, not the data itself.

• Stored on the heap.

• Contain references (memory addresses) to their data.

• Assignments copy references.

Example:

class MyClass { public int Value; }
MyClass obj1 = new MyClass { Value = 10 };
MyClass obj2 = obj1; // obj2 references the same object as obj1
obj1.Value = 20; // obj2.Value is also 20