Explain Managed and Unmanaged Resources in c# code example

Example: managed and unmanaged resources in c# examples

public class ManagedAndUnmanagedObject : IDisposable
{
    private SqlConnection sqlConnection = new SqlConnection();
    private UnmanagedHandle unmanagedHandle = Win32.SomeUnmanagedResource();
    private bool disposed;

    public void Dispose()
    {
        Dispose(true); // client called dispose
        GC.SuppressFinalize(this); // tell the GC to not execute the Finalizer
    }

    protected virtual void Dispose(bool disposeManaged)
    {
        if (!disposed)
        {
            if (disposeManaged)
            {
                if (sqlConnection != null)
                {
                    sqlConnection.Dispose();
                }
            }

            unmanagedHandle.Release();

            disposed = true;
        }
    }

    ~ManagedAndUnmanagedObject()
    {
        Dispose(false);
    }
}