This question, in form or another, is often asked in the gospels- which are the various accounts of Jesus' life. Jesus usually answers the question with a parable, which I would like to attempt.
The Kingdom of God is like a flash mob; people from all walks of life coming together at a time in history (some call it a kairos- you can Google it) and join in singing the praises of God. Some found the noise irritating for they had much on their minds. Others found the music soothing and the music offered a break from their studies. Still other found their souls and joined in the celebration, and, for a moment, joined in something larger than themselves.
The Kingdom of God still happens today. It happens when people come together and buy backpacks for kids whose life's circumstances are challenging, it happens when people spend time with people to laugh and cry- to grieve but also to celebrate, it happens when people of conscience join their voices together to speak out against the evils of life. The Kingdom of God is a beautiful thing, open to all people. I hope you join in the singing.
The song in the video is called, "Wana Baraka" and the words roughly translated are, "They have a baraka (gift), ushini (victory), and upendo (love), for those who in fellowship come to Jesus.