Cultural resource projects are usually performed on behalf of someone — a developer, a government agency, a utility, or another firm — and the client field records that party's name as free text. Filling it in makes it easy to see at a glance who a project is for and to group or report on the work you have done for a given client. It is optional, so internal or speculative projects can leave it blank. The plain-text client field is separate from clientId, which holds a structured identifier when the client also exists as a record in another system; you can use one, both, or neither.
Technical section
Data model, API, and internals — visible to developers.