How to know whether Mac has SSD or HDD installed
- Apple Menu -> About This Mac -> System Report
- Select Storage in the Hardware section
- Select "Macintosh HD" on top
Alternatively you can run system_profiler SPSerialATADataType
or system_profiler SPStorageDataType
in Terminal which more or less gives you the same information
Apple Menu -> About This Mac -> System Report -> Hardware -> SATA/SATA Express
For my MacBook Pro (Early 2015) this showed the Serial-ATA Device Tree, from which I was able to get the model number for my SSD. This related question, How to get serial number from Mac hard disks? might help if you think you have an HDD.