This review of modem interpretations of nature and physiological significance of EEG alpha activity was inspired with the following aims: 1--alpha activity phenomena determination, 2--summering the experimental and theoretical data about the nature, origin and neurophysiological mechanisms of the alpha oscillations distribution, 3--description of the most famous brain alpha activity structure hypothesis, 4--presentation of authors hypothesis about EEG alpha activity indices as: 1--individual alpha peak frequency in parietal-occipital brain area, 2--alpha spindle features: length, amplitude variability and steepness, 3--reactivity to visual stimulations as: amount and time duration of amplitude suppression and frequency range width in which amplitude suppression is appeared.