What does `DeploymentItem` attribute mean?

When create the unit test class for this class, Visual Studio create a test method with the attribute DeploymentItem. This means that the item is copied to the 'TestResults\Out' folder and is basically an artifact/necessary item for the test run. Thus, it is stored apart from the bin directory and does not get overwritten. This is especially useful when running the tests in different environments (build server, no hard-coded paths...) and of course it is necessary to make the tests repeatable

/// <summary>
///A test for Add
///</summary>
[TestMethod()]
[DeploymentItem("ConsoleTryIt.exe")]
public void AddTest()
{
    var expected = 122;
    var actual = Program_Accessor.Add(1, 121);
    Assert.AreEqual(expected, actual);
}