Audacity is best known for being a free audio recorder and editor for quite a long time. One of its most appreciated features is that is simple yet very good audio editor which don't take up much of the space of hard drives.
It supports Windows, Mac, and Linux. Besides its great feature one problem is that they don't have any support team, but they do have a forum with people willing to help you out.
If you are new to audio recording and editing, this is the to-go product for you.