Preliminary

[Sarah]

Introductory; previous; preceding the main discourse orbusiness; prefatory; as, preliminary observations to a discourse orbook; preliminary articles to a treaty; preliminary measures;preliminary examinations.

[Sarah]

happening before something that is more important

[Mark Zuckerberg]

“denoting an action or event [preceding] or done in [preparation] for something [fuller] or more important”

So pretty much something that happens in preparation for an event or action.

[Dave Paprocki]

coming before a more important action or event, especially introducing or preparing for it:

[Magaret]

Preceding or done in preparation for something fuller or more important.