Civil Service jobs are assessed with Success Profiles, the framework every department uses for recruitment. It can test five things: behaviours (how you work), strengths (what you enjoy and do well), ability (usually online tests), experience (what you've done before) and technical skills or qualifications. Each advert says which of these the job uses, and whether they're tested in the written application, at interview, or both.
There are nine behaviours: Seeing the Big Picture, Changing and Improving, Making Effective Decisions, Leadership, Communicating and Influencing, Working Together, Developing Self and Others, Managing a Quality Service, and Delivering at Pace. An advert picks a handful of them, usually not all nine. Look for the list of behaviours in your advert. Those are the questions you'll get.
Your written application is usually scored first, in a stage called the sift. If you pass the sift, you're invited to interview, often on Microsoft Teams or another video call. A small panel asks the questions, takes notes, and scores each behaviour separately. Many departments score each answer out of 7, and 4 is the usual pass mark, but check your candidate pack because it varies.
Strengths questions are different. They aren't published in advance, they're quick, and they ask how you feel about things (“What kind of work gives you energy?”) rather than for an example. You can't prepare scripted answers for them, and you don't need to. Answer honestly and briefly.