There are 4 human goals divided by our scripture:
1. Artha, security.
2. Kama, sense pleasure.
3. Dharma, ethics / duty.
4. Moksa, freedom.
The first three purusaartha are dealt within the Karmakānda and moksa is dealt within the Vedānta.
The limitation of the results of these first three pursues are said by Sruti itself.
Therefore for one whose pursue is the freedom from limitation, knowledge of the Self which is the content of Vedānta is the means.
Paths of Yoga
There is no others independent path to gain moksa. To be free from the Ajnānam (ignorance about my true nature), the only way is through knowledge which is the path of Jnāna Yoga.
How about others path?
Karma Yoga which is doing actions with attitude of offering to the Lord and receiving the result of the actions with gratitude. By Karma yoga attitude, one gain mental purification.
Bhakti Yoga the devotion toward the Lord. Without bhakti there is no Karma yoga, and for a real bhakta, he converts any action in to Karma yoga. Because of taking into consideration some specific actions like Japa and Kīrtana etc, Bhakti yoga is specified. Raja Yoga a path of self discipline and practice which result is steadiness of the mind.
They are preparatory means by which one become fit for knowledge.