Ideas, concepts and the like are mental object. A mental object is just something some of us call any of these. When we look at something, we create a mental object of that item in our mind, when we thing about something, or even an action, feeling, each are mental objects.
It is to these mental object that we react, not the object it's self. Until this is established in our minds, we flail.
A common mental object is god. It is not a real object, but a mental object. Thinking it is real makes the effect real to us. But this is just an example. Now that we know it for what it is, we can move on.
Now, we can say that desire to indulge in food is also a mental object, and it is the desire that must be looked at to suppress it. It is the job of reason to crush desire into something suitable for human consumption.
The ego is a defence structure which automatically defends us against anything that could change our thinking, and create a "problem" for us to resolve. It was created in the mind by the mind and is just another mental object that springs into action of defence. It means nothing. What are we? A collection of mental objects, plus a body.
The concept of a mental objects puts life into perspective. It is the foundation for moving forward into the new world of tomorrow, that is entirely unknown. We react only to mental objects, and the words are just dull pointers to the idea. There are many pointers, and many handles. The handle I have grabbed is mental object.
Mental objects go through a "conversion matrix", and some come out as "volitions" or actions, other take up other parts, like verbs, or modifiers. Some just stimulate other mental objects that cause pain. But these too, are mental objects. we can see them as mental objects and let go of them, and accept that which is, and move on.