Three names cover three different situations: huisartsenpost, spoedpost and 112. Parents of small children, and anyone newly arrived without a settled GP relationship, tend to face this decision first at two in the morning, when the wrong pick costs either hours of waiting or an escalation nobody needed.
Life-threatening — chest pain, difficulty breathing, severe bleeding, someone unconscious or unresponsive — is 112, no hesitation and no need to check with anyone first. Urgent but not immediately dangerous, outside your huisarts's (GP's) normal opening hours — evenings, nights, weekends, holidays — is the huisartsenpost, sometimes branded "spoedpost" in certain regions; the two names cover the same out-of-hours GP service. Think a sudden high fever in a small child, a deep cut that needs stitches, or pain that's clearly serious but you're breathing fine and conscious. You call first rather than walking in; a triage nurse asks questions and either books you an appointment, sends someone out, or tells you it can wait until your regular huisarts reopens — and if what you describe sounds like it needs an ambulance, they escalate that themselves. During normal weekday hours, your own huisarts's practice is always the first call for anything short of 112-level, even same-day, since they know your history and it avoids an unnecessary trip elsewhere. If you're ever unsure which bucket something falls into, calling the huisartsenpost's triage line is a reasonable default outside office hours — worst case they redirect you, which is a much better outcome than guessing wrong in either direction.