The Chakras are essentially the main energy centers of the body, each corresponding to a different aspect of your body. Although there are hundreds of Chakras, the 7 main ones are the Root, Sacral, Solar Plexus, Heart, Throat, 3rd Eye, and Crown. It is believed that when these Chakras are 'open,' they positively benefit your life, but when they are 'closed, under active, or overactive' they can be the source of imbalance in your daily life.
Here are the Chakras in order, with a brief description.
Root: This is the chakra that is the basis for all the others. It represents your will to survive and live.
Sacral: This chakra represents your feelings and sexual desires.
Solar Plexus: This chakra is corresponds to your leadership skills, and ability to communicate in a group.
Heart: This chakra represents love, compassion, and kindness.
Throat: This is the chakras corresponding to communication, and the expression of yourself.
Forehead/3rd Eye: This is the chakra for intuition, and your 'sixth sense.'
Crown: This chakra represents your connection with divinity, your spirituality, and your wisdom.
This website can tell you more about each:https://www.mindbodygreen.com/0-91/The-7-Chakras-for-Beginners.html
When you look on people's profiles and they have each of the chakras with a percentage listed next to them you are looking at the results of their chakra test, which can most commonly be found on this website:http://www.eclecticenergies.com/chakras/chakratest.php
Be mindful though, the chakra test is not entirely accurate, and is mostly just a fad that has existed on this site for many years. The test gives you a score ranking from -100% to 100%, calculated by you answering 50 questions or so. If you do decide to take the test, be mindful that being 'overactive' (above 75%) is not a good thing, you want balance.