Who is Lord Krishna?
Today, Lord Krishna is known and worshipped in two forms, as the Baal Krishna (child Krishna) and as Yogeshwar Krishna. The only person who truly understands Lord Krishna is the Gnani Purush (self realized person), for such a person has the same awareness of the soul as Lord Krishna. Such Gnanis are extremely rare.
Many think that Lord Krishna fought wars, killed many people, had sixteen thousand queens and lived a leisurely, luxurious worldly life. In the said scenario, why is he considered God ? Why do people all around the world worship him so devoutly?
In reality, God (i.e. the Soul) had manifested in Lord Krishna. In other words, he was a Self-Realized being. He had constant awareness of being a Pure Soul; (the constant awareness that, "The body is separate and I am a Pure Soul".)
Despite his physical involvement in worldly affairs, he always had the awareness that 'I am not the 'doer' of anything. Although he had so many queens and lived a rich and palatial life, he was in fact 'Naishthik Brahmachari' (one who is detached from all worldly passions and no inclination towards sexual passions.) He lived with the awareness that he could not escape his karmas and that he had no choice but to undergo the effects of his karma, with awareness.
The Essence of 'The Gita'
Before the great war of the Mahabharat Lord Krishna said to Arjun, "Arjun, you have been with me for a long time, but still you haven't known me in the true sense. What you see in front of you is not the real me; what you see is the physical body. I am separate from this body. I am a Pure Soul. You too, are a Pure Soul. Your brothers, uncles, gurus and friends with whom you are about to fight, are also Pure Souls. This (fighting) is your destiny (karma), so you have to carry it out with this awareness of the Soul. If you remain in this awareness and fight the war, you will not bind any new karmas and your remaining ones will be exhausted. This will lead you to ultimate salvation."
Thus, Arjun remained in the awareness Lord Krishna gave him. He killed many great men but still did not bind a single karma and achieved ultimate salvation in the same life.
The Celebration of Janmasthmi (birthday of Lord Krishna) takes place at all Trimandirs, with special programmes including bhakti.