Freeform supports some popular Webhook integrations as well as generic ones too. All webhook integrations are managed inside the Webhooks CP area under Settings (not inside Composer or elsewhere).
The following Webhook integrations are currently available for Freeform Pro only (click each one for individual setup instructions):
Every integration is a little bit different, so we have detailed instructions for setting up each integration on their own page.
Check out the developer documentation for more information about making your own custom webhook types.