What it is
Instead of your app asking "did anything happen yet?" every so often, the webhook notifies you the instant it occurs: an event (for example "payment received") is sent to the URL you configured.
Why it matters to an agency
It is what triggers real-time automations between GoHighLevel, n8n, Make and your tools. Without webhooks, everything would be slower and more manual.
Example
When a form is submitted on your website, a webhook notifies n8n, which creates the contact in GoHighLevel instantly.