Krshna Janmashtami, also known as Shri Krshna Jayanti, Gokulashtami or just Janmashtami is celebration of birth anniversary of Lord Krshna. You may say birthday of Lord Krshna. It is one of the important annual festival for Hindus, which falls on the ashtami tithi of krishna paksha of Hindu luni-solar calendar. That is the eighth day of the dark fortnight in the month of Shravana [July-August]. On that day Krshna was born at midnight in Mathura, few millenniums before Christ.
According to Hindu scriptures the Supreme Lord, who is absolute and without beginning expands himself into unlimited forms and manifest in different forms, re-incarnate as Sage or Superhumanbeing or something else as required for the situation. Krshna is one such incarnation of supreme God-head Lord Vishnu in human form. The main purpose of incarnation of Supreme God-head is to annihilate
unrighteousness, re-establish righteousness and arouse moral values and super consciousness every where, show the path of morally-right and peace to people. Now let us look at a couple of verses from the scriptures to see how this is narrated.
7th verse in Chapter 4 of Bhagavad Geeta
Yada yada hi dharmasya glanirbhavati bharata
Abhyuthanamadharmasya tadatmanam srjamyaham
Abhyuthanamadharmasya tadatmanam srjamyaham
Which means
'Whenever and wherever there is decline in moral values or
righteousness, and predominance of immorality or unrighteousness, then
at that time I will manifest.'
8th verse in Chapter 4 of Bhagavad Geeta
Paritranaya sadhunan vinashaya cha dushkrtam
Dharmasansthapanarthaya sambhavami yuge yuge
Which means 'For
the protection of virtuous people and for the destruction of evildoers, and to re-establish morality and righteousness, I manifest myself millennium after millennium.'
25th verse in Chapter 10 Canto 1 of Bhagavatam
dhathe bhagam satyamrtam dayam yasho bhavaya roopani dadhadhuge yuge.
Which means 'Whenever
there are rulers and administrators living like untamed wild animals in the lowest
modes of existence, the Lord in his transcendental form manifests His
supreme power, the Truth Positive, shows special mercy to the faithful,
performs marvelous activities and manifests various transcendental forms
as is necessary in different periods and ages.'So,
Lord Krshna was one of those manifestation/incarnations of Supreme Lord, who came as Krshna to
annihilate the atrocities and misery caused by demons and evil-doers, of that time, like Putana,
Shatakasura, Trinavartha, Aghasura, Bakasura, Kamsa, and others, whom he destroyed and protected lawful people from those evil-doers and goons.
Right from childhood Krshna displayed many supernatural powers and with that relieved people from many troubles. He educated people about 'dharma', righteousness and devotion. He taught people to practice constant unconditional selfless pure love, but never to fall in love with any [which means love all but be detached]. To show compassion to all living beings and never make others suffer. To be free from arrogance, pride, self-admiration and practice simplicity, humility and selflessness. Life's desire should not be for sense gratification, one should desire only healthy living and self preservation. Human life is meant for finding absolute truth. And so on.
The Krshna Janmashtami festival is celebrated all over the world by Hindu community. Many special functions and ceremonies are performed in Krshna temples.