Wifi and Internet are not the same thing, although most people use the terms interchangeably.

Wifi is a radio signal that is emitted from your wireless router. It is a signal that can travel 50+ feet in radius from your router. It's also known as your wireless network name or SSID (e.g., NETGEAR99). What this wifi signal does is acts as a "wireless wire" between your router and your devices (e.g., computer, laptop, iPad, smart phone, etc.). This allows you the freedom to move around your house without dragging a long computer cable around with you.

All of your wireless devices have a wifi signal strength meter (aka signal bars). The closer your device is to your router, the more signal bars you will have. Alternatively, the further away from the router your device is, the fewer signal bars you will have. The fewer signal bars you have means the weaker your device's connection is to your router, and the slower any activity will be when your device requires the router to perform a function (e.g., like connecting to a network printer, surfing the Internet, casting from your device to a TV, etc.).

So, a strong signal just means your device is closer to your router. But it doesn't mean that you have a strong Internet signal. Think of your router as a table lamp. The closer you are to the lamp, the stronger the light is.

NOTE: To fix a weak wifi signal, explore wifi boosters or a mesh router system (like Netgear Orbi).

The Internet may be thought of as an extensive, inter-connected database of information. Like walking in to a "World library."

Your router is what connects all of your devices to the Internet and to each other. For example, you might have a wireless printer. As long as your printer is connected to your router's wifi and your device is connected to your router's wifi, you can print! But if either the printer or your device is not connected to the router, then you cannot print (unless your printer is cabled directly into your computer). The router is the go-between between devices, the Internet, etc.