Indigo children exist. They are special but no more special than any child, different in ways but really no more different than any child.
Generally indigo children trust themselves more than adults because, even at a young age, they can easily see that adults are controlled by selfishness, have power control issues, and are too easily addicted to things (smoking, alcohol, drugs, food, sex, work...) that they use to cope with life.
Adults also form barriers (religious, country, state, county) where there should be none and they join groups (religious, sports...) to get a sense of betterment and belonging when they should feel this way without having to join a group.
Indigo children have a very mature sense of what is truly right and wrong and because of their inherent mistrust of adults indigo children tend to be very independant. They would rather volunteer at a homeless shelter than go to Disneyland. They would rather plant a garden than just about anything. Generally they are more interested in art and music than most other children and have a sense of spiritualness that, to them, is overpowering.
Some of them absolutely "know" they are the child of God. Sometimes the parents of these children feel like there is an invisible wall between them and their child, because there is.
If you want to try to understand them, get out of your comfortable group and instead choose to see everything as one big group, stop abusing substances, stop worrying about things that truly don't matter to the universe, and relax in a lawn chair and enjoy the sunset with a smile.