Audacity is an open source multi-track recorder and audio editor with limited DAW capabilities. Its intuitive interface and wide variety of plugins and effects makes it great for editing or creating sound effects. While it is not built as a traditional DAW, it is possible to do some basic non-destructive editing. It is simpler and more approachable than many other audio editing packages. It is available for Windows, Linux, and Mac.Audacity Website
Audacity is perhaps more intuitive to non-audio people than most dedicated audio programs. There are no massive, intimidating mixing consoles, it doesn’t proudly show off virtual faders and knobs all over the UI. Drag an audio clip in, draw a simple volume envelope, go into the effects menu and change pitch, export. For simple tasks, it’s really easy here.
Using Audacity for extensive work, however, proves difficult. It is not possible to hear real time changes as you adjust effect parameters. The fact that track meters are not visible by default sums up its use as a multi-track editor: there are no non-destructive effects and no keyframing.