If my iPhone were to be monitored, what would be monitored exactly?

Can my activity be monitored? Say, I'd be using an application, whatever it may be. Could someone monitor my activities on a certain application? How does it work exactly? Can they monitor my screen? I don't know if whatever I'm saying is making sense, lmao. If it's not obvious, I'm not very techs-savvy.

I believe that generally apps you install can't monitor your screen unless your device is rooted, because they don't have sufficient permission for that.

But when you install an app you see what permissions it asks for.

Don't worry about it, just be wise when you install apps, if it seems very suspicious don't install it.

Update: I see you wrote iPhone, I was thinking about Android, so I don't know if it works same for iPhone.

If how you use the phone, and what programs you use, couldn't be monitored, why would anyone do it! EVERYTHING you do, everything you say and everything you type can be monitored.

Anything can be monitored. Through the router you can easily log every site you go to, and everywhere it goes.

They can monitor your calls, texts, gps, etc.