A codec (Coder/Decoder) converts analog signals to a

digital bitstream, and another identical codec at the far

end of the communication converts the digital bitstream

back into an analog signal.

In the VoIP world, codec's are used to encode voice for

transmission across IP networks.

Codec's for VoIP use are also referred to as vocoders,

for "voice encoders".

Codecs generally provide a compression capability to save

network bandwidth. Some codecs also support silence

suppression, where silence is not encoded or transmitted.

Regards