The portfolio most people mean when they talk about an interior design portfolio is a graduate portfolio. A hardcopy (which usually has a digital copy) of student work showcasing your design “talent” from your recent studies. In my opinion, the only time you ever need a graduate portfolio is if you want to get a job with an interior design or architecture firm and you’re preparing for an interview straight out of university. That’s it. I am not going to discuss how to create this type of portfolio here (that’s what I’ve included in the video above). This really is a niche portfolio and the one thing I typically teach that you don’t need if you want to work with real clients. Also, my graduate portfolio, although it did land me excellent jobs, never landed me or any interior designer I’ve known (or taught) a paying client, so I’d say it’s the least useful type of portfolio for many of the designers who are trying to start a business (my area of expertise).
If you’re interested in creating a digital or printed interior design or architecture portfolio and you’re graduating from design school and looking to get a job, alongside the video above, I would have a look at this book, which is the best one I’ve read on the topic and specifically written for this purpose. “Portfolio Design For Interiors By Harold Linton and William Engel” (not an affiliate link).