Development goals are personal growth goals an employee sets and tracks - a certification, course, skill, project, or mentoring relationship - each with a target date, a progress percentage, and optionally a cost and training platform (e.g. a specific course provider).
Approval: goals can require approval (pending -> approved/rejected) so a manager or HR can sign off, for example when there's a cost attached.
Evidence: you can attach evidence (files/links) once a goal is complete, and track supporting notes throughout.
Development requires the Professional plan tier or above (it's a distinct entitlement from Engagement surveys, even though both live under people growth).