Search under 'bilirubin' and your quest will be more productive. ;-)
Bilirubin is, in general terms, an end product of the destruction of red blood cells. Newborn babies have lots and lots of extra red blood cells because they needed them while they were in the womb (this is complicated to explain, but essentially it's because they need them to draw enough oxygen from their mother's blood). Once they are born, a lot of these cells are destroyed--so it is normal for babies' bilirubin levels to rise in the week or so after birth.
However, we don't want them to rise too high, because if they get over a certain level they can damage the brain. Bilirubin is taken up and recycled by the liver, but some babies' livers are not working quite efficiently enough when they are born, so we have to help them keep down their bilirubin for a few days. Fortunately, this is usually very easy--we just put the baby under a special lamp for a few hours a day until the levels go down! Blue light can break down the bilirubin instead.
Hope this helps.
4th year medical student.