Your ISP internet service provider has ways of looking up your browsing history and looking at what websites you're on and what content you're downloading.
However ISPS do not have the time or manpower to watch what everyone is downloading on their service and unless you're doing something really illegal they really don't care.
If the ISP happens to notice you're downloading too large of files and going through a lot of data that is more than normal in a short period of time then the ISP may take a look and either terminate your service or throttle your internet connection.
But other than that unless the authorities summon the ISP to look up your history and provide it to them the ISP doesn't really look at what you're doing online because it would not be feasible for them to do so because of all the people using their service.