Retina 4k 21.5 inch
3.4 GHz Quad-core Intel Core i5
16GB RAM / 2400 MHz DDR4
1TB
You didn’t give enough details, but if it’s the 21-inch model, it probably doesn’t have an SSD.
Check under ‘More info’
That model can come with a 1TB Fusion Drive or you can configure it with a 1TB SSD. To know for sure, open Disk Utility and see if there's one drive or two listed.
Probably not. Most of the ones I’ve seen have Fusion drives.
It’s likely a Fusion drive.
It's easy to add an SSD to that if needed