The [Checked] attribute is used to mark a method or a method invocation as being "checked", meaning that the method applies extra runtime checks such as bounds checking or other parameter or state validation
Generally used as a per-method optimization, [DisableObjectAccessChecks] will avoid the runtime per-object-access checks which by default are only applied in debug builds anyway
The [Unchecked] attribute is used to mark a method or a method invocation as being "unchecked", meaning that the method omits runtime checks such as bounds checking or other parameter or state validation