Unauthorised access to a computer, its files and programs by a 'hacker', a computer expert who can break through its security.
Hard Drive is the permanent storage space where all your documents, photos, music, etc. are stored. It is long term memory and stays in place when you switch off your computer.
The 'front page' of a website, where you're told what's on the site, how to get around it and how to search for things that might interest you.