First a few definitions to get us started:
Wi-Fi (also spelled Wifi or WiFi) is a popular technology that allows an electronic device to exchange data wirelessly (usingradio waves) over a computer network, including high-speed Internet connections. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards". However, since most modern WLANs are based on these standards, the term "Wi-Fi" is used in general English as a synonym for "WLAN".Many electronic devices such as laptop computers, smartphones, tablet computers (iPad, iPod, etc) and other devices can connect to the Internet if there is a wireless network access point or hotspot. The WiFi detectors are built into the device. To establish a WiFi network, you need to have a standard network connection from an Internet service provider. In a home network, after signing up for Internet service, that connection is usually made by some sort of physical connection to the service. For example, my service provider run a cable from the local network connection into my house. Next, you need a device to connect to the service provider's network, usually a net modem. A net modem is essentially a box with connectors on the back or side. To use a net modem for your home network, you need another box called a router. These routers either with or without wireless connections or with both plug-in and wireless capability.
OK, so you get Internet service, then you attach a net modem. Many service providers will "rent" you a net modem to go with your service, just like the cable TV box that you get with Cable TV service. If the service requires you to use their net modem, you have no choice, but usually, you can buy your own net modem and save the cost of paying the service provider rent. You will also have to purchase a router to connect to your net modem. Be sure and buy one that has a Wireless Local Areal Network (WLAN), also called WiFI, capability. There is some amount of technical setup to establish a local network for your home. You may need to have some help from someone who has done this before.
Once you have your Wireless Local Area Network (WLAN) set up, you have "WiFi. That means you can establish a WiFi connection to your local router. When you set up such a network, it is absolutely necessary that you create a secure network that requires a password to establish a connection. Otherwise, you will be providing free Internet service to anyone within range of your router.
Once your local network is established, any WiFi enabled device, iPad, Kindle, laptop, etc. should be able to "see" the network. If so, all you have to do is turn on the WiFi option on your device and then establish a connection to the network using your password. Don't forget the password or you will have to start the whole process over again.
If you have a WiFi enabled device such as an iPad or smartphone, you probably already know that you can connect to any number of local area networks or WiFi Hotspots, for free around the country. If you have WiFi turned on in your device, you just have to turn on the device to see if you have a WiFi signal. Many libraries, fast food restaurants and other businesses establish WiFi Hotspots for promotional or public service reasons.
As I mentioned in the beginning of this post, WiFi can make you life interesting. If you travel a lot, you likely already know that finding a reliable WiFi Hotspot can be hit and miss. There are programs that will search for WiFi connections and alert you, but most of the time, you just have to search for a signal from your device. Some places, such as the Atlanta Airport, will have very limited WiFi service for free, but may charge you for a full Internet connection. Hotels may also offer free WiFi as part of their services.
You can always pay for a device to connect directly to the Internet, using a cell phone service such as AT&T or Verizon or others, but there is a considerable expense for a network data connection.
Depending on a WiFi connection can be further interesting because the signals are "local." They can be really local, like only working in one room of a building. If you have a problem in your own home finding the WiFi signal, you may have to buy yet another box, a WiFi Repeater, that will extend the reach of your WiFi router.
I have been using WiFi connections to make my presentations at genealogy conferences, but I have found them to be very unreliable, even when I have paid for the service. For that reason, I am moving away from live presentations and depending more on PowerPoint presentations.