Wi-fi is the acronym for Wireless Fidelity, essentially a set of standards for transmitting data over a wireless network.
Wi-fi allows you to connect to the net at broadband speeds without cables, as long as you have the right equipment and, in most cases, a regular internet service provider and a wi-fi account.
How does it work?
Wireless uses radio waves of a particular frequency - in this case 2.4Ghz - to send and receive data. It is the same frequency on which microwaves, cordless phones and Bluetooth devices work - which can cause interference between these gadgets when used in conjunction on the same channel.
Radiowaves such as wireless, are a type of radiation, called non-ionising. This radiation includes microwaves, infrared light, mobile phone communications and visible light.
Ionising radiation, such as X-Rays, can be destructive to biological tissue, and can cause DNA damage in cells.
Non-ionising radiation does not carry enough energy to ionise atoms and at high levels of exposure can only excite atoms, causing heating.
This is the process by which microwave ovens heat food, by exciting the molecules that are exposed to the radiation.
A typical microwave oven has 100,000 times the radiation intensity of a wi-fi network.
What are the concerns over wi-fi safety?
Some scientists have reported that low levels of non-ionising radiation can cause damage to chromosomes. But there is currently no scientific evidence that wi-fi, in particular, causes this to happen.
There is speculation that low level radiation can do more than just excite atoms, a non-thermal interaction., but again there is no current evidence to suggest this is possible.
Recent concerns over mobile phone use and children - the UK government recommends that young children do not use mobiles as their skulls are thinner than adults - have given rise to concerns over wi-fi.
The Health Protection Agency points out that a person sitting in a wi-fi hotspot for a year would be exposed to only the same amount of radiation from a 20-minute mobile phone call.
So is wi-fi 100% safe? Scientists distinguish between a current lack of evidence to show that wi-fi is unsafe and definitively saying something 100% harmless.
Some people have called for more research into wi-fi, to prove that it is safe.
But it is impossible to prove a negative, scientists point out; there is no way of demonstrating that wi-fi has zero effect on someone.
Should I err on the side of caution and stop using wi-fi?
The World Health Organisation says there is no risk from low level, long-term exposure to wi-fi networks.
However, Professor Lawrie Challis, chairman of the Mobile Telecommunications and Health Research (MTHR) programme management committee, encourages young children not to use a computer on their lap and to place it on a table.