ware: A piece of data. Typically a filesystem tree. (A .tar file can handled as a ware.) Wares are stored content-addressably.
content-addressable: The practice of giving data a name based on its own content. Typically implemented by using a cryptographic hash over the content. Content-addressable systems are immutable.
formula: A document describing a series of wares, how to arrange them in a filesystem, some action to perform on them, and what parts of the filesystem to save as resultant wares. Wares in a formula are referred to by their content-addressable hash, meaning formulas in turn are an immutable description of how to set up and run something. Repeatr evaluates formulas.
catalog: A named record pointing to one or more wares. Catalogs associate the name to the ware's hash, and are usually cryptographically signed. Catalogs are a mutable structure, but also continue to carry references to previously-referenced wares even when updated.
commission: A document naming a series of catalogs, how to arrange their referenced wares in a filesystem, some action to perform on them, and which catalogs should be updated to refer to new wares saved from parts of the resultant filesystem. In other words -- like formulas, but connected to catalogs instead of directly to wares.