A Brahmin are the class of the society who are responsible to carry on the ancient vedic culture. Brahmins were designated as the priestly class, serving as priests and spiritual teachers. They are carrying on the old vedic scared knowledge and also all the important teaching. They are the well aware about all the shastras and Vedas.
Who could be a real Brahmin is really a tough question. Here is a way in Sanskrit teaching which describe the true identity of a Brahmin. Who are actually the roots of Indian culture.
विप्रो वृक्षस्तस्य मूलं च सन्ध्या
वेदः शाखा धर्म कर्माणि पत्रम्|
तस्मात्मूलं यत्नतो रक्षणीयं
छिन्ने मूले नैव शाखा न पत्रम्||
Vipro vrukshastasya moolam cha Sandhyaa,
Vedah shaakhaa dharma karmaani patram.
Tasyaanmoolam yatnato rakshneeyam.
Chinne moole naiva shaakhaa na patram.
my own scriblling mandala art
Vipro = a wise and learned Braahmana.
Vrukshastasya = Vrukshah + tasya.
Vrukshah = a tree.
Tasya = its.
Moolam = the root.
Cha = and.
Sandhyaa = the deity presiding over the three divisions of the day, and religious ritual performed by Brahmanas.
Vedah = the four Vedas - Rigveda, samveda, yajurveda and atharvaveda, the Sacred scriptures of Sanaatana Dharma.
Shaakhaa = branches.
Dharma karmaani = religious rituals.
Patram = leaves.
Tasyaanmoolam = Tasmaat + mooolam
Tasmaat = therefore.
Yatnato = with special care and effort. Rakshaneeyam = to be guarded or protected
Chinne = on being cut off.
Naiva = hardly, no.
"A wise and learned Braahmana is like a tree and its roots are performing the ritual of 'Sandhya Vandan"(chanting the'Gaayatri Mantra' thrice every day in the morning, noon and evening), the four Vedaas are like the branches of this tree and performing various other religious rituals are the foliage of this tree. Therefore, it is the sacred duty of every Braahmana to take special care and effort to protect the roots, because if the root is cut off neither the branches nor the leaves of the tree will survive."
The scholar actually wanted to remind the importance of the role played by Brahmans in propagating and preserving the Sanatan Dharma. If they do not do so there is the
danger of Sanatan Dharma becoming extinct.