What is a Placebo group?

In medical research, scientists need to know if a new medication is effective; so, during testing, they give one group the actual medication and one group a placebo (a sugar pill, that looks like medicine). Neither group is told which one they are getting. In the end, the hope is that the group that received the medicine will feel much better than the group that just got the placebo. Sometimes, though, there is not much difference, at which point the researchers know the medication probably is not effective enough.