WiFi allows mobile devices (tablets, smart phones, etc.) and other computing devices to communicate wirelessly over a computer network using radio waves.
Using a WiFi connection mobile devices can access the Internet through a wireless network access point or hotspot so long as they are within range of the access point. An access point can be part of a router or a standalone device that is typically connected to a router.
Wireless network access points usually have a very sort range of about 15 - 30 meters and can be hampered by walls and other physical barriers. However, the range of an wireless network access point can be extended using repeaters and reflectors which bounce or amplify radio signals.
A cellular or mobile network is a radio network that allows mobile devices (smartphones, tablets, etc.) to communicate wirelessly with one another over a wide geographic area.
Data plans can be purchased from cellular network providers (ex. Bell, Rogers, Telus, Wind Mobile, etc.) giving users access to the Internet over a cellular network. However, cellular signals may be spotty or non-existant in some buildings and rural areas.
Mobile-friendly website: A website that is specially formatted to be readable and useable on the smaller screen of a mobile device.
Often these mobile sites are just stripped down versions of a standard website and users may be automatically redirected to the mobile version if they access the site using a mobile device.
Mobile sties do not require a download. Mobile sites are accessed by using the Internet browser on the mobile device. One important difference from an app is that since it is a website, you will always need an Internet connection to access the content of a mobile site. There is no offline availability of information.
Mobile sites are not device specific. In other words, they are designed to be accessed from any mobile device. The webpages that make up a mobile site are formatted differently than a regular webpage.
Characteristics of a mobile site: less images, formatted for a smaller screen, load faster, and may have less content than the regular website.