SWP v1 Format Specification
SWP is a file format used to describe per-tag patches for an SWF file. It is designed to make it possible to apply patches in-stream, without having to keep more than a single tag of an SWF file and the SWP file's index in-memory at a time.
An SWP file is a container consisting of multiple patches. The word "container" here refers to the SWP file, "patch" to an individual entry within it, "SWF" to an SWF file (duh) and "tag" to a tag within said SWF (see the SWF spec). "Payload" is ambiguous, and should always be qualified as "tag payload" or "patch payload" in this context.
Everything is Little Endian. The SWF format uses little endian, and so does every platform on which Flash Player runs.