How can I use webhooks for tracking subscription actions in my app?

[ssodano]

I'm developing an app that offers on demand service and subscription service. There is both a free plan and paid plans. How can I use webhooks to listen to the actions that the merchant takes on different plans (subscribe/upgrade/downgrade/renew/cancel)? I would like to understand which are the topics to listen to for create subscription, renewing the subscription, canceling the subscription.