Interleaved audio
A layout for multichannel audio where samples from each channel alternate, left-right-left-right, rather than living in a separate buffer per channel.
An interleaved stereo stream is a sequence of frames: one sample per channel at the same instant, then the next frame. That is how WAV files and most sound cards store data, and it suits streaming from disk. The alternative, usually called planar or non-interleaved, gives each channel its own contiguous array, which is handier when you filter one channel at a time or want to run SIMD across it.
APIs went different ways. ASIO and JACK hand over one buffer per channel, Core Audio supports both, and in FFmpeg the planar formats give themselves away with a trailing p, as in fltp. Mixing them up does not crash anything; it plays the audio at half speed with the channels scrambled, which is much more confusing to debug.