What is the true concept of 'GURU' in Hinduism & Sikhism?

I agree with Sikh soldier. As you said Bani Guru Guru Hi Bani ( I hope I got it right) means that The word of god is the Guru and the Guru is the word of god ( I think). Since Guru Gobind Singh Ji said there will be no more human Gurus, that the Guru Granth Sahib Ji is our eternal Guru, this means that Guru Granth Sahib JI is the word of God for Sikhs. And Yes GGSJ does communicate with us through the words of God ( through a Hukamnama).