"As part of your examination in a course, you have been asked to verbally explain the concept of CSS (cascading style sheets). Describe what they are, how they're used, and why they came out." Doesn't need to be a whole essay, one paragraph will do

What program is this in?

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.