What is AMR?
The Adaptive Multi-Rate (AMR) standard is a speech coding algorithm that operates on narrowband signals (~200 to 3400 Hz) at variable bit rates in the range of of 4.75 to 12.2 kbps. This technology was initially developed for the GSM system and later adopted by the 3GPP as the mandatory codec for 3G wireless systems based on evolved GSM core networks (WCDMA, EDGE, GPRS). AWB stands for Adaptive Multi-Rate Wideband ACELP speech codec.

What is MP3?
MP3 stands for MPEG Audio Layer 3, which revolutionized digital music. Derived from the audio sections of the MPEG-1 and MPEG-2 video specifications, MP3 compresses CD-quality sound by a factor of roughly 10, while retaining most of the original fidelity. MP3 files are played on the computer via media player software, such as Apple's iTunes and Microsoft's Windows Media Player, as well as in countless iPods and other handheld players. While 128 Kbps (kilobits per second) is considered the norm for MP3 files, MP3s can be encoded to bit rates from 8Kbps to 320 Kbps. The higher the bit rate, the better the sound and the larger the file.