Coder is the short form of coder-decoder, a computer program/algorithm that is designed to encode and decode audio and video signals into sequences of binary data or raw digital bitstream. Nyquist’s Pulse or PCM is a type of codec which reduces a large file to a manageable file size for storage. MP3 is a well known codec used for digital audio storage and playback.
A container format is a file format the bundles a codec in order to keep the separate audio and video data together during processing for an end-user. The most common containers used are .wav for the Windows operating system and .aiff formats for Apple operating system. Both container systems are not structurally different because the coder or PCM audio stream doesn’t change once the container opens in a CD player. The container “talks” to the operating system to let it know what kind of data is inside and how to uncompress it.