Okay, explained like you’re a five year-old (well, okay, maybe a bit older), without too much oversimplification, and (hopefully) without sounding too biased:

What people call “Obamacare” is actually the Patient Protection and Affordable Care Act (abbreviated to PPACA or ACA). However, people were calling it “Obamacare” before everyone even hammered out what it would be. It’s a term that was, at first, mostly used by people who didn’t like the PPACA, and it’s become popularized in part because PPACA is a really long and awkward name, even when you turn it into an acronym like that. Barack Obama has since said that he actually likes the term “Obamacare” because, he says, “I do care”.

Anyway, the PPACA made a bunch of new rules regarding health care, with the purpose of making health care more affordable for everyone. Opponents of the PPACA, on the other hand, feel that the rules it makes take away too many freedoms and force people (both individuals and businesses) to do things they shouldn’t have to.