Email is a single way to communicate.
SMS/MMS is another using totally different communication protocols provided by cell phone companies, that depends on the cellular networks.
Apple’s Messages, is again a totally different communications protocol between Apple devices, that depends on the based Internet.
Meta’s WhatsApp, is similar to Apple’s Messages, but uses its own communication protocols. As does Signal, Telegram, Facebook Messenger, etc…
Twitter, X, Threads, Mastodon, BlueSky, etc… also different protocols.
Real-Time apps such as FaceTime, Skype, Zoom, etc… are a different protocol.
Websites, such as discussions.apple.com, Discord, Facebook, youtube, tiktok, Slack, etc… are similar, in that they use standard HTML features, so most browsers can work with them, but the HTML from each service is unique.