Is the concept of disk and hard disk the same?

Not the same concept. The two are at cross purposes with each other.

A disk, a tape-like device in a computer's external memory, contains round magnetic disks in a square, sealed box, which is designed to prevent scratches on the disk's surface that could lead to data loss. There are soft disks and hard disks. A hard disk is a mechanical hard disk.

A hard disk is one of the main storage media of a computer and consists of one or more disks made of aluminum or glass. The disks are covered with a ferromagnetic material. Hard disk has solid state drive (SSD disk, a new type of hard disk), mechanical hard disk (HDD traditional hard disk), hybrid hard disk (HHD a new hard disk based on the birth of the traditional mechanical hard disk).SSD uses flash memory particles to store, HDD uses magnetic discs to store, hybrid hard disk (HHD: Hybrid Hard Disk) is the magnetic hard disk and flash memory integrated into one kind of hard disk. Hybrid Hard Disk (HHD: Hybrid Hard Disk) is a type of hard disk that integrates a magnetic drive and flash memory. The vast majority of hard drives are fixed drives, permanently sealed and secured in a hard disk drive.