These ADF components don’t talk directly to the ACS and APS backend services. There are some layers between them that are worth knowing about before you start coding. The ADF components talk to ADF services, which in turn talks to the Alfresco JS API , which internally calls ACS and APS via their respective ReST APIs. You could use the both the ADF services and the Alfresco JS API directly from your application if there is no ADF component available to do what you want. In fact, you will quite frequently have to use the ADF services in your application to fetch content nodes, process instances, task instances etc.
The following picture illustrates the architecture of an ADF solution:
The ADF components and services are implemented in Angular, which in turn is implemented in TypeScript. The Alfresco JavaScript library is pure JavaScript and could be used with any other JavaScript framework.