The AVC shortcut means Advanced Video Coding (also known as H.264/MPEG-4 Part 10) video encoding file format. The video data encoded with this codec typically uses MKV, FLV, M4V, MP4 and other file extensions instead AVC so any program accepting these formats as well can usually perform avc to avi conversion.
However, when you convert AVC video to AVI format, the video quality may be decreased, because AVI doesn't support HD video resolution.