What are the differences between delegates and events?

What are the differences between delegates and an events? Don't both hold references to functions that can be executed?

An Event declaration adds a layer of abstraction and protection on the delegate instance. This protection prevents clients of the delegate from resetting the delegate and its invocation list and only allows adding or removing targets from the invocation list.

To understand the differences you can look at this 2 examples

Example with Delegates (in this case, an Action - that is a kind of delegate that doesn't return a value)

public class Animal
{
    public Action Run {get; set;}

    public void RaiseEvent()
    {
        if (Run != null)
        {
            Run();
        }
    }
}

To use the delegate, you should do something like this:

Animal animal= new Animal();
animal.Run += () => Console.WriteLine("I'm running");
animal.Run += () => Console.WriteLine("I'm still running") ;
animal.RaiseEvent();

This code works well but you could have some weak spots.

For example, if I write this:

animal.Run += () => Console.WriteLine("I'm running");
animal.Run += () => Console.WriteLine("I'm still running");
animal.Run = () => Console.WriteLine("I'm sleeping") ;

with the last line of code, I have overridden the previous behaviors just with one missing + (I have used = instead of +=)

Another weak spot is that every class which uses your Animal class can invoke the delegate directly. For example, animal.Run() or animal.Run.Invoke() are valid outside the Animal class.

To avoid these weak spots you can use events in c#.

Your Animal class will change in this way:

public class ArgsSpecial : EventArgs
{
    public ArgsSpecial (string val)
    {
        Operation=val;
    }

    public string Operation {get; set;}
} 

public class Animal
{
    // Empty delegate. In this way you are sure that value is always != null 
    // because no one outside of the class can change it.
    public event EventHandler<ArgsSpecial> Run = delegate{} 
        
    public void RaiseEvent()
    {  
         Run(this, new ArgsSpecial("Run faster"));
    }
}

to call events

 Animal animal= new Animal();
 animal.Run += (sender, e) => Console.WriteLine("I'm running. My value is {0}", e.Operation);
 animal.RaiseEvent();

Differences:

1. You aren't using a public property but a public field (using events, the compiler protects your fields from unwanted access)
2. Events can't be assigned directly. In this case, it won't give rise to the previous error that I have showed with overriding the behavior.
3. No one outside of your class can raise or invoke the event. For example, animal.Run() or animal.Run.Invoke() are invalid outside the Animal class and will produce compiler errors.
4. Events can be included in an interface declaration, whereas a field cannot

Notes:

EventHandler is declared as the following delegate:

public delegate void EventHandler (object sender, EventArgs e)

it takes a sender (of Object type) and event arguments. The sender is null if it comes from static methods.

This example, which uses EventHandler<ArgsSpecial>, can also be written using EventHandler instead.

Refer here for documentation about EventHandler