The concept of Chakras was first used by the Hindu and Buddhist religions and is now commonly used in several alternative medicines. The idea is that there are points where supposed 'Meridian lines' intersect and these can be used to have an effect on different parts of the body by some form of manipulation. There has never been any evidence for these meridian lines or chakras. Despite this, the popularity of these ideas has not changed. The most famous chakra is the 'Third eye chakra' which is supposedly located in-between the eyebrows.
Chakras are closely aligned with acupuncture - Practitioners claim they release 'blockages' at certain chakra points, increasing the flow of 'energy'. Maps of the body showing where these lines intersect and where to put needles are used to treat patients for a variety of ailments.
Some practitioners cite scientific evidence for the claims of chakras existence, but it is often based on incredibly shaky foundations.