In this quickly growing world of technology, people have become so addicted to smartphones, tablets, iPods and this entire virtual online world that they sometimes don’t even realize that they exist in a real world. Since these device don’t work on food and water there comes this huge issue of giving power to these devices and thus comes the term charging of the batteries present in these devices and as soon as the word charging comes our head becomes full of tangled wires. So to deal with this, now scientists have developed a new technology for wireless transmission of power. It basically works on a concept called RESONANT INDUCTIVE COUPLING. This concept is very easy to understand so please don’t be scared and astonished by hearing such a complicated term. Actually to understand this concept you only need your 12th std physics. So there are basically three words ‘resonant’, ‘inductive’ & ‘coupling’. Let us revise the meanings of these words in context of physics.
Firstly resonance, in simple words resonance happens when the amplitude of a wave (in this case an electrical signal) maximizes at a certain frequency. In our case this is important as we want to ensure maximum electrical power transfer.
Now electromagnetic induction, in our case we are talking about mutual inductance which in short is just induction of voltage or an emf in a coil when a variable current carrying coil is kept in its vicinity.(of course lesser the distance higher the induction)
Last but not the least coupling is just used as both the coils are electrically coupled (not physically).
So now if you take all these three things together in your mind as one joint concept then I believe your previous review of the term being complicated will change a bit. 
Hence by this I guess you can easily understand how power can be transmitted wirelessly and so nowadays whatever wireless chargers you see simply just consist of two coils one is the transmitter and the other one is the receiver. High frequency (resonant frequency) signals are first generated before the transmitter and then after the receiver receives the signal, the signal is rectified to whatever DC output is required for the device.(high frequencies are used so as to decrease the losses through the air i.e to decrease the leakage flux)
There are a lot of advantages as we can see there is no need to deal with the long and tangled wires, and we don’t even have to stay very close to our power sockets.
One more big benefit is that we can simultaneously charge one or more devices with just one setup as you can see in the figure beside-
But on the downside there is also a fact that we have to make a great sacrifice on efficiency as we increase the distance between the two coils the leakage flux through the air increases which in turn decreases the power transferred. Another problem is the range of the distance at which the two coils are kept because after some distance there will be no power transmission but for that a solution that is being proposed is that we create a network of all the transmitter coils at suitable distances so that the receiver can receive power suitably from all the coils.
Also there are alternate options available other than resonant inductive coupling like Conductive Connections, Radio Transmissions and Wi-Fi.