Odds are this is the routine Program Integrity (PI) interview, which is a routine part of the process.
Prior to Covid ALL adult applicants were subject to the PI interview, but this was suspended as part of the measures to facilitate processing in response to Covid. Over the course of the last year it has been apparent IRCC is increasingly resuming the routine interview procedure. The applicable PDIs (Program Delivery Instructions) still state that ALL adult applicants
must be interviewed, subject to the measures implemented "Due to COVID-19," which cancelled most interviews. There are many indications that IRCC is on a path to get back to requiring ALL adult applicants have a PI interview (with some exceptions of course).
The PDIs, including the Guide for citizenship applications page 4, state during the interview the "citizenship official" will
- check your language skills, if you’re between 18 and 54 years of age
- verify your application and original documents
- ask any questions we may have about your application
- make sure you meet all the requirements for citizenship
There is a huge range between what is typically/routinely asked versus what MIGHT be asked. Language skills verification is usually accomplished just through the casual Q&A of the interview. The email should have described what documents to bring (if the interview is in person) or be prepared to present (if it is an online interview), but in general these are just the originals of the copies the applicant submitted with the application.
Most applicants report a quite brief and mostly casual Q&A. While the scope of questions asked can be very broad, even those who are questioned more at length generally describe it as NOT challenging, not at all confrontational, just some questions about who you are, where you live or have lived, where you work or have worked, maybe a few family related questions. A few, very few, have reported more confrontational questioning, such as where the official conducting the interview has doubts or suspicions about a particular issue, with the applicant's physical presence being the sticky point in many of these scenarios (which, it is worth emphasizing, are unusual, not what most applicants encounter, not close).
If you are scheduled for an in-person interview, it is worth noting that some forum participants have reported they were given the opportunity to participate in an oath ceremony very soon after the interview, like the same day or within a couple days. No idea what percentage of applicants are getting this opportunity (odds are it is only a small percentage), but many of those who have were most pleasantly surprised.
