Just a Mum needing info on hard drives 🇦🇺

Hi everyone, I have basically no clue about anything gaming or tech related but I am in the market for an external hard drive for my son who has a PS5 digital version console.

I did a bit of a search on reddit but all that SSD, HDD, TB stuff makes zero sense to me and most threads don’t have specifics items/brands/websites to explore. So please comment with specific products I can look at especially if you know of a place having a good sale at the moment.

Also, when I went to JB Hi Fi (Australia btw) they told me that the Seagate was literally the only one you could use on the console. Is that true?