Akshay Kumar is named Pakshi Rajan in the movie. His name means the King of birds.He is named because of his love towards birds. After an incident in his childhood, he decides to dedicate his life to birds and becomes an Ornithologist. His home is a habitat to hundreds of rare species of birds and sparrows. This dedication created love in birds towards him. He loved them equal to his own life. But after some turn of events and over usage of mobile phones and increased radiation, many birds started dying. So, he hated mobile phones.
The main source of power for Pakshi Rajan is his Aura. Aura is a type of coloured radiation which enclose human body, a place or an object. It is a paranormal concept. In simple words, it is the influence a person has over some region around them. This exist even after one's death. In the film, Dr.Vaseegaran (Rajinikanth) explains briefly How to reference material written by others what is aura and mentions that Pakshi Rajan's aura is spread over kilometers. Due to the immense love showered on them, the dead birds aura also added to the aura of Pakshi Rajan and increased power day by day. As he hated cellular phones and towers causing radiations, he primarily targeted mobile phones and controlled them using his power. But controlling mobile phones isn't his only ability. He can also control other persons (without their consent) and objects. It's the same reason he could possess any human being (shown at the very end of the official trailer at 2:04) and turn high radiation from cell phone towers towards Foot ball (Soccer) stadium.
Though Wikipedia mentions it's a new age belief, there are several mentions of this concept in different traditions and cultures with different names since ancient times. There are stories about Buddha where his presence made the people around him peaceful and non violent. Even predators and preys forgot the enmity between them and lived with harmony.
However, the aura emitted by him was negative (causing damage and destruction) and was neutralized in the end.