Hi RedRaven4231965. Yes, disc = hard drive - either the older type with spinning disks (HDD), or the newer solid-state drives (SSD).
I recently purchased the standard version from the MS Store, so your installation options will be a little different than mine - see Zendesk’s Steam Install Guide - but I expect the required available disk space will be very similar. The following applies to my MS store install:
The install is in two parts:
A) The core program, at a little over 2 GB, and
B) The game packages (aircraft, airports, terrain data, etc).
Once the core install is downloaded, it starts up the Installation Manager (see pic below) to download the game packages. As you can see from the screenshot below, my install required 159.83 GB. Yours may be somewhat higher as the Premium version includes additional aircraft & airport scenery.
The Installation Manager installs the latest version of the game (v1.35.21.0), The thirteen optional world updates will take up approximately an additional 113 GB of disk space - so ~ 273 GB, in line with the response by MSFSRonS
Right now, my core install, packages and world updates #1 & #2 take up 166 GB on my hard drive.
In addition, you can, post install, choose to configure a rolling cache and manual cache. For example, I’ve configured a 5 GB rolling cache & 150 GB manual cache.
Then there are all the additional paid, free & community addons you can optionally download & install…
MSFS is indeed a HUGE program. I’d suggest at least 200 GB of available free space (if you do not want to install any optional packages), and 300 GB or more if possible if you want the world updates too. Either way, I believe the install also needs some temporary space during the install to decompress the downloaded compressed packages before moving them into their final locations, so just having the absolute bare minimum may cause the install to fail at some point if it runs out of disk space.
If you are looking at purchasing a new desktop computer, just search for “New PC Help” in these forums. For example see this post.
Lots of folks have asked for advice over the years on what to buy & got tons of helpfully ideas & comments. If you have specific questions about what to buy, or if a specific PC you see online or in a store would work for MSFS, post a thread with the specifications & folks will be happy to tell you if they think it will work or turn out to be a lemon.
Hope this help answer your question, though I think may still be unhappy 