Computers connected to the web are called clients and servers
Communication between the client and server are done through requests and responses
A simplified diagram of how they interact might look like this:
Typically user-facing devices connected to the internet:
Computers
Mobile devices
Smart Speakers (Amazon Echo, Google Home)
Smart Appliances (Ring Doorbell, Nest Thermostat, etc)
A computer dedicated to run services to serve the needs of other computers; examples include the following:
Web server (stores and delivers files needed to generate web pages)
Database server (stores and delivers data)
File server (stores and delivers files)
Print server (sends and receives print jobs)
Home media server (stores and delivers video and/or audio)