You are describing either 1) an Electron app; 2) A website; 3) A shortcut
Of course an Electron app or a website are similar to what I describe because it all uses web technologies for the ui frontend, which always means some kind of browser. You could even argue if an electron app is just some kind of website.
But again.. not sure what you are getting at and if you tried to answer my question.
This is how I do slack and a ton of other apps. Just type the name, no need to recall the URL. You can do this with multiple subpages on the same URL as well