What is "deep cleaning" compared to regular, twice a year dental cleaning?

it's what happens when there hasn't been regular 'twice a year' cleaning since before the dental hygenist was born. We had a laugh about that, she asked how long it had been since my last cleaning, and when i told her she laughed and said 'So, longer than I've been alive." So, it took about twice as long as the 'twice a year' variety.