Wi-Fi is just a catchy term used to refer to wireless networks. A long time ago, the only way to connect devices was to run network cables from one to another to create a local area network or LAN. It was unsightly and inconvenient and meant that you were tethered to a location where there was a cable.
Wi-Fi is a type of wireless networking that allows you to connect two devices without the use of cables. You still have access to the network, but not to the physical connections. The component in charge of these links is generally a router. Your gadgets may collaborate through the router. Data, print, and stream files stored on one device may be accessed by other devices connected to it via Wi-Fi. That's a local area network (LAN) that isn't linked to the Internet.
An Internet connection enables your computer to interact with data on remote servers operated by companies around the world. The data might be text, pictures, video, or something else entirely. Your computer uses its modem to dial a telephone number online, and the person on the other end of the phone (typically another modem) establishes a connection.
An Internet service provider (ISP) is a company that provides the data connections through which your computer exchanges information with remote servers. Your ISP can be a local or national phone company, but increasingly ISPs are cable TV companies as well. The former broadcasters have all moved their operations into telecommunications because they want to provide television, telephone services, and broadband connections over one network infrastructure at the same time.