In this sutra, Patanjali gives the goal of yoga. If the restraint of the mental modifications is achieved, the one has reached the goal of Yoga.
Patanjali has given the definition of Yoga and at the same time the practice.
“If you can control the rising of the mind into ripples, you will experience Yoga”
Citta is the sum total of mind. Within the Citta are different levels. The basic mind is called ahamkara , or the ego, the I. This gives rise to the intellect or discriminative faculty which is called buddhi. Another stage is called manas, the desiring part of the mind which gets attracted to outside things through the senses.
A little example about Citta. Read more if you are a cheese lover.
You are quietly sitting and enjoying your solitude when a nice smell comes from the kitchen.
The moment the “manas" records, there is a delicious smell somewhere.
The “buddhi" discriminates, what is that smell? I think its cheese. How nice, What kind of cheese? Swiss? Yes it is swisss cheese. The same I ate one my visit home last year.
“Ahamkara" says, oh is it so? Then i should have some right now.
These three things are happen one at a time, but so quickly that we seldom distinguish between them.
These modification give rise to the effort to get the cheese. The want was created and, unless you fulfill it by going to the kitchen and getting some your mind wont go back to its original peaceful condition. The want is created. These Citta Vrttis are the modifications of the mind that disturb that peace.
I hope you enjoyed reading - I am going to get my piece of cheese and continue my practice of Yoga again tomorrow.
With Love Karin
Reference: Tantras of the yoga sutras (Alan Finger), The yoga sutras of Patanjali (Sri Swami Satchindandanda)