What is the difference between a reference type and value type in c#?

Your examples are a little odd because while int, bool and float are specific types, interfaces and delegates are kinds of type - just like struct and enum are kinds of value types.

I've written an explanation of reference types and value types in this article. I'd be happy to expand on any bits which you find confusing.

The "TL;DR" version is to think of what the value of a variable/expression of a particular type is. For a value type, the value is the information itself. For a reference type, the value is a reference which may be null or may be a way of navigating to an object containing the information.

For example, think of a variable as like a piece of paper. It could have the value "5" or "false" written on it, but it couldn't have my house... it would have to have directions to my house. Those directions are the equivalent of a reference. In particular, two people could have different pieces of paper containing the same directions to my house - and if one person followed those directions and painted my house red, then the second person would see that change too. If they both just had separate pictures of my house on the paper, then one person colouring their paper wouldn't change the other person's paper at all.

Value type:

Holds some value not memory addresses

Example:

Struct

Storage:

TL;DR: A variable's value is stored wherever it is decleared. Local variables live on the stack for example, but when declared inside a class as a member it lives on the heap tightly coupled with the class it is declared in.
Longer: Thus value types are stored wherever they are declared. E.g.: an int's value inside a function as a local variable would be stored on the stack, whilst an in int's value declared as member in a class would be stored on the heap with the class it is declared in. A value type on a class has a lifetype that is exactly the same as the class it is declared in, requiring almost no work by the garbage collector. It's more complicated though, i'd refer to @JonSkeet's book "C# In Depth" or his article "Memory in .NET" for a more concise explenation.

Advantages:

A value type does not need extra garbage collection. It gets garbage collected together with the instance it lives in. Local variables in methods get cleaned up upon method leave.

Drawbacks:

1. When large set of values are passed to a method the receiving variable actually copies so there are two redundant values in memory.

2. As classes are missed out.it losses all the oop benifits

Reference type:

Holds a memory address of a value not value

Example:

Class

Storage:

Stored on heap

Advantages:

1. When you pass a reference variable to a method and it changes it indeed changes the original value whereas in value types a copy of the given variable is taken and that's value is changed.

2. When the size of variable is bigger reference type is good

3. As classes come as a reference type variables, they give reusability, thus benefitting Object-oriented programming

Drawbacks:

More work referencing when allocating and dereferences when reading the value.extra overload for garbage collector

I found it easier to understand the difference of the two if you know how computer allocate stuffs in memory and know what a pointer is.

Reference is usually associated with a pointer. Meaning the memory address where your variable reside is actually holding another memory address of the actual object in a different memory location.

The example I am about to give is grossly over simplified, so take it with a grain of salt.

Imagine computer memory is a bunch of PO boxes in a row (starting w/ PO Box 0001 to PO Box n) that can hold something inside it. If PO boxes doesn't do it for you, try a hashtable or dictionary or an array or something similar.

Thus, when you do something like:

var a = "Hello";

the computer will do the following:

1. allocate memory (say starting at memory location 1000 for 5 bytes) and put H (at 1000), e (at 1001), l (at 1002), l (at 1003) and o (at 1004).
2. allocate somewhere in memory (say at location 0500) and assigned it as the variable a.
   So it's kind of like an alias (0500 is a).
3. assign the value at that memory location (0500) to 1000 (which is where the string Hello start in memory). Thus the variable a is holding a reference to the actual starting memory location of the "Hello" string.

Value type will hold the actual thing in its memory location.

Thus, when you do something like:

var a = 1;

the computer will do the following:

1. allocate a memory location say at 0500 and assign it to variable a (the same alias thing)
2. put the value 1 in it (at memory location 0500).
   Notice that we are not allocating extra memory to hold the actual value (1). Thus a is actually holding the actual value and that's why it's called value type.