Because we can only see some visible light with our eyes, it takes practice with our minds to perceive the aura. The aura will first appear as a hazy outline around the hands and fingers. You can see lines of energy jump from one finger to another and as the mind is trained you will be able to se more of the aura's many colors and depth. The aura body is comprised of many planes which vibrate at a high and low frequency. The higher frequency is connected to our spiritual needs and the lower frequency is connected to our material needs.
Many psychics can see the esoteric body as the auras on the outside and the chakras on the inside.
Vibrations and frequencies can also determine peoples moods which can be felt when you come in contact with them. If you notice you can pick up their mood, if they are having a good day, you can feel their vibration, and you feel up, when it is a bad day and negative, you can feel your frequency or vibration be drained by them, which then in turn transfers to you, and you then can pick of their feeling of negativity even in short contact.