On the basis of the Sadhaks (one who practices spirituality), interest and authority there are 3 paths (Sadhana Marg) demarcated in Buddhism.
To eliminate misery of life, a Sadhak of the 'Shravak Yan' learns the pre-determined methods in the tutelage of an experienced teacher (Guru) and aims to attain the state of 'Arhat'. The ultimate aim of his Sadhana (penance) is to achieve Bodhi or 'Parmarth Jnana' (knowledge of eternal truth) and free himself from all miseries and sorrows. Using his talent and strong determination, the Sadhak moves ahead on the Sadhana marg to attain the state of Bodhi, despite not having a Guru. He is known as 'Pachchek' or 'Pratyek Buddha'.
Sadhakas who belong to this category, stay away from material life, meditate in solitude and lead detached lives. They do not reach out again to the multitudes to impart their knowledge or to encourage them on the path of Boddhimarga. They are indifferent to preaching or the Bahaiya (external) Karma.
PACHCHEK BUDDHA SAYAMEVA BUTHANTI, PARE NA BODHANTI.
Sadhaks who attain state of Pratyek Buddha or knowledge of Bodhi do not go around preaching and encouraging people towards their goal. On the contrary, Sadhaks belonging to the Bodhisattva Yan do not attain Buddhatva (enlightenment) merely to put an end to personal sorrows and miseries, they aim at putting an end to sorrows of all living creatures and animals.
After being enlightened, they work in the best interest of all the living beings i.e. 'SATVARTH KRIYA'. It is said about those who follow the Bodhisattva Yan and attain enlightenment:
BUDDHA SAYAMEVA BUJJHANTI PARE CHA BODHENTI ||
The Budha Loga attain Bodhi and encourage others to follow the similar path for their wellbeing and emancipation.
Shravak Yan and Buddha (Pratyek) Yan are generally known as 'Hinayana' while Bodhisattva Yan has been known as Mahayana. We shall quote a shloka from the Bhagwat Gita to demarcate the difference of ideology within Hinayana and Mahayana.
Devotee Prahlad tells Bhagwan Narsimha -
PRAYENA DEVA MUNAYAHA SWAVIMUKTI KAMA MAUNAM CHARANTI VIJANE NA PARARTHNISHTHAHA |
NAITAN VIHAM KRUPANAM VIMUMUKSHA EKO
NANYAM TWADASYA SHARANAM BHRAMATO ANOPASHYE ||
Meaning - O Lord! Inspired by the concept of salvation, sages and hermits often observe silence and go into the forest and live in total solitude. They do not strive for others' welfare. I do not want to leave all these poor innocent people and attain liberation. In this world, a person falls prey to all types of good and bad situations and becomes confused and aimless. In this way, such people in dilemma do not have any refuge other than you.
These types of people known as Shravaks and Pratyek Buddha have resemblance to the people mentioned in the above shloka.
Those people, who strive for enlightenment of themselves along with the emancipation of all living beings by emancipating them from all sorrows and miseries, are known as Boddhisattva.
To attain state of enlightenment, the Boddhisattva takes the following resolution.
"I shall enlighten myself and also help others to emancipate and enlighten themselves. I shall attain salvation and help others in their liberation. I shall cross this ocean of miseries (Material Life) and help others to do so."
The incantation recited for the initiation into the Buddhist fold is
BUDDHAM SHARANAM GACHCHAMI
DHAMMAM SHARANAM GACHCHAMI
SANGHAM SHARANAM GACHCHAMI
Meaning:- I seek the refuge of Buddha I seek the refuge of the Dharma I seek the refuge of the Sangha.