Which device is used to convert digital data into analog data and then back into digital data in order to send the data through a phone line?

Modem might be the answer

You must indent the items

I’d say platform as a service (paas) or application platform as a service (apaas) or platform base service is a category of cloud computing services that provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app.