Interleaved
Definition
A stereo audio file format in which left and right channel data is stored in a single file, with samples alternating between channels. Contrasted with dual-mono, where each channel is a separate file.
In Simple Terms
A stereo audio file where both the left and right channels live inside one file. This is how you'll almost always export and deliver your mixes — one file, two channels.
In Practice
A stereo mix bounced as an interleaved WAV contains both channels in a single file — the standard delivery format for most mastering and distribution workflows.