Gia Milinovich is a science writer who has access to a pretty good physics resource - her husband, Science 2.0 fave Dr. Brian Cox.  But even Cox, who can make sense of why E=MC^2, can't help with what radiation means.  So Milinovich did it herself in 2006.  The problem?  The site is dead.

Enter the Wayback Machine and we get some good stuff even if the original server is gone.   We will singlehandedly keep Milinovich from suffering through Invisible Wife Syndrome.

She wrote:
The Becquerel measures how much activity there is in a quantity of radioactive material. A measurement of one becquerel means that in a particular quantitity of material one nucleus is decaying per second.

The Gray measures the physical effects of radiation or how much energy is absorbed per unit mass of matter. One gray is equal to one joule of energy deposited in one kilogram of matter.

The Sievert measures the amount of damage radiation does to biological tissue. As one gray of different types of radiation can have more or less effect on the human body, the sievert is used as a ‘dose equivalent’.
Fine, but what does any of that mean to non-experts?   In a style certain to make Dr. Cox envious, she likens them to pop singer waif Kylie Minogue and Sweet Science brute Mike Tyson.   Who would you rather be punched by?

The number of times they hit you (the becquerel), she says, may not matter as much as how hard (the gray) and if they do any damage (Sievert).   She notes that the average annual radiation dose in the UK is 0.0027 Sv (2.7 mSv) and a traveler will get half that radiation dose on a flight from the UK to Spain.

Full article, for as long as it exists.