If your website or app depends upon a service managed by a third party, you have a service dependency.
Service dependencies enable e-commerce (like PayPal or Stripe), scheduling (like Google or Calendly), performance (like your CDN), and many (MANY!) other capabilities. External services are key to building any modern and competitive project. Without well selected (and well supported) services, even the most attractive design won't get your project very far. But service dependencies also incur a challenging risk: They leave you dependent upon third party operations over which you have no influence.
To manage your service dependencies efficiently and effectively, you need to know each and every one of them well. You need to stay abreast of developments in each of the services, and it's industry and regulatory contexts. You need know how to drive all aspects of the service to which you have been granted access. You need to know when to ask for help and how to ask for it. Or, if you want to actually attend to your own mission, the mission that your project is intended to support, you can hire someone to do all this heavy lifting for you.