I've no doubt that someone will give you a really good explanation... but in the meantime, "Controlled Airspace" is a particular type of airspace with defined limits both horizontally and vertically within which an air traffic control service is provided and all aircraft are subject to ATC clearances. Uncontrolled airspace is much of the space outside CAS where pilots can largely fly without ATC clearance. However, even in those areas, ATC units provide a separation service to pilots who wish to participate by warning them of other traffic andaircraft flying in the immediate vicinity of aerodromes will be "contrtolled". Controlled Airspace does not always start at ground level and the high flying commercial jets you see will be in Class A Controlled Airspace and subject to ATC clearance with separation from all traffic.
I'm not aware of any web site where you can find live information about aircraft flying over you. A gadget called SBS "Virtual radar" is available to plug into your PC and this will display aircraft using a particular type of on board radar equipment called ADS-B. However, not all aircraft transmit the required information so will not be displayed. There are web sites where flights may be viewed on a map but they rely on the information I've just mentioned and it's usually delayed by 5-10 minutes for security reasons. Try
www.openatc.com but don't expect to see any military jets on there!