The M4A format (AAC) was designed as the successor to MP3. At the same bitrate (e.g., 256kbps), an M4A file sounds cleaner than an MP3. For Avril’s gritty vocals on “Losing Grip” or the acoustic delicacy of “I’m With You,” M4A preserves the "air" around the guitar strings.
I'm assuming you're referring to the album "Avril Lavigne" (also known as "The Best of Avril Lavigne" or simply "Avril Lavigne") released in 2003, but I couldn't verify a widely recognized album or song specifically titled "Life m4a" by Avril Lavigne. Avril Lavigne Life m4a