In the point of “Indriya, Mana, Buddha and Aatma”, we saw how our bodily system is divided into different layers of Indriya, Mana, Buddha and Aatma, with innermost layer Aatma being the ‘real self’, hidden behind those layers.

This same concept is described in Taittiriya Upanishad, using Pancha koshas (five layers). The koshas are: 
1. Annamaya Kosha : This is our physical body 
2. Pranamaya Kosha : Breath/chetna that keeps physical body alive.
3. Manomaya Kosha: Layer of mind, which controls physical body.
4. Vijnanmaya Kosha: Layer of Intelligence, which learns and analyzes things, and helps us decide how to behave in various situations.
5. Anandamaya Kosha: Layer of eternal happiness. The real self (Aatma) is hidden inside the Anandamaya Kosha.

Additionally, The layers are also divided into three types of bodies. 
1. Sthula sharir : Made of Annamaya and Pranamaya Kosha, representing our physical body, which we are currently using in this life.
2. Suksham Sharir made of Manomay, and Vijnanmaya kosha. This is the controlling engine for the Sthula sharir, and decides how we act/behave.
3. Karan-Sharir, made of Anandamaya Kosha. This is the reason why we are born, and it carries the karma/vasana/gunas across various birth-and-death cycles.

Again goal of this classification is to identify how our decision making work, so that we can control our behaviors and finally help us get on the path of spiritual progress. 

Many people find these details “too technical”, but it is not meant for everyone.. Its for people who are inclined to make spiritual progress using logical analysis. 

Most of us, who have studied science have been taught to logically analyze everything before accepting it, so these methods of spiritual progress are for folks like us.

But there are many who don’t want to get into these details and feel these details are distractions for spiritual progress. For them, there are many other paths like Karma, Bhakti, which doesn’t need anyone to get into these logical analysis stuff, and still achieve same destination.

Hinduism has something for everyone, so choose what works best for you.

All the Best!