The Buddhist doctrine of anatta is tied to the idea that people should let go of all worldly desires that they have in order that they might eventually reach the state of nirvana. The term "anatta" refers to all of these worldly things.
Anatta is all the things that are not truly part of the self. This includes everything that we perceive with our senses. What is truly the self is simply our soul. Everything else is anatta. In order to reach enlightenment, we need to let go of all anatta. We must let go of our desires because they are the things that frustrate us and bind us to life. We must let go so that we can stop our cycle of rebirth and instead achieve nirvana.
This technical Buddhist term means all "beings" are composed of transient natures or changing forces, too quick to see with the ordinary eyes, so much so that they are void of substances or soul. The Buddha advises us, in our search for highest truths, to note the present changing materialities and mentalities (nama and rupa). Universally all puthujjanas, the uninstructed human beings, take these ultimate realities to be permanent entities and they think souls, entities, individualities and selves really exist in the ultimate sense. Thus the wrong belief, the Sakkayaditthi belief in personality or eternal soul, is the hardest and greatest obstacle to achieve mental and spiritual peace.