Difference between destructor, dispose and finalize method

Destructor implicitly calls the Finalize method, they are technically the same. Dispose is available with objects that implement the IDisposable interface.

You may see : Destructors C# - MSDN

The destructor implicitly calls Finalize on the base class of the object.

Example from the same link:

class Car
{
    ~Car()  // destructor
    {
        // cleanup statements...
    }
}

The Destructor's code is implicitly translated to the following code:

protected override void Finalize()
{
    try
    {
        // Cleanup statements...
    }
    finally
    {
        base.Finalize();
    }
}

Your understanding for the Destructor is right:

From MSDN

The programmer has no control over when the destructor is called because this is determined by the garbage collector. The garbage collector checks for objects that are no longer being used by the application. If it considers an object eligible for destruction, it calls the destructor (if any) and reclaims the memory used to store the object. Destructors are also called when the program exits. It is possible to force garbage collection by calling Collect, but most of the time, this should be avoided because it may create performance issues.

In C# terms, a destructor and finalizer are basically interchangeable concepts, and should be used to release unmanaged resources when a type is collected, for example external handles. It is very rare that you need to write a finalizer.

The problem with that is that GC is non-deterministic, so the Dispose() method (via IDisposable) makes it possible to support deterministic cleanup. This is unrelated to garbage collection, and allows the caller to release any resources sooner. It is also suitable for use with managed resources (in addition to unmanaged), for example if you have a type that encapsulates (say) a database connection, you might want disposing of the type to release the connection too.