When you become enlightened, you will have no doubts about the
truth/reality/our true nature, that you have awakened to... as my
experienced friend said "this is more Real than real". Such
Insights gained through Buddhist practise will completely shatter
your previous illusions and perspective of yourself and the
world... and you will be in awe that reality is really quite
different from our everyday consciousness and what we used to think
reality is. They will describe an awakening into non-duality of
subject and object, where the illusion of a separate permanent
'self' is seen as an illusion, and an all pervading infinite pure
Presence/pure awareness is experienced, transcending thoughts and
perception, time and space, space-like, like the vast sky,
boundless, etc etc... and that Buddha Nature is ONE with all
sentient being's, Buddhas and Bodhisattvas' Buddha Nature and the
Dharma Nature of the entire universe.. we, all phenomena, are EQUAL
in essence... like clouds, vapour, ocean, river, are all made of
the same substance... water. It has One Taste... and that is our
true self, who we really are, pure awareness, the clear light that
illuminates everything but itself featureless, formless, and many
other endless descriptions, etc. Buddhist teachings such as
"Emptiness", "No Self", "Non-Duality", "Intrinsic Luminosity",
"Nirvana", or even other descriptions such as "Consciousness",
"Pure Awareness", "Tao", "Brahman", "Keter", "Buddha Nature",
"Buddha Mind", "One Taste", "Christ Consciousness", "God",
"Godhead", "Allah", "The Kingdom of Heaven Within", "Spirit", the
"I AM that I AM" or our "true self that is no self", whatsoever,
and all these poetic metaphors and attempts as descriptions are
finally directly understood at an experiential and intuitive level,
with no possibility of doubts. As a result of such
insights/awakening one attains liberation, bliss, clarity which is
lasting and carries on throughout one's life and forever.
Therefore, an enlightened person will know he is enlightened. A
Bodhisattva practitioner however does not stop at his own
liberation, but vows to help other sentient beings and complete his
training in the perfections of the 10 paramitas (the ten virtues)
and eventually to attain perfect Buddhahood.
I am not enlightened yet (I've only been a Buddhist for a few
years... and just turned 17
)... so I
can only paraphrase others' descriptions. But even before this
great awakening, we can see many benefits from Buddhist practise..
including more awareness of ourselves (i.e our own thoughts and
behaviors) and others (compassion, love, forgiveness, etc), more
calmness, happiness, more liberated, fearless (like overcoming your
fears of death), etc. Life wld be different if one practises the
dharma. As I said before, "Once you have a taste of how practicing
dharma results in, you will never be able to resist the path, you
can't forget it, you can't discard it. There is a natural
compulsion to continue practicing all the way to
enlightenment."