The Macintosh SE from 1987 was part of the second generation of Macintoshes, coming out at the same time as the Macintosh II. However unlike the Macintosh II the SE was an all-in-one computer like the first Macs. The SE had a number of improvements compared to earlier Macs: for a start it used the new Apple Desktop Bus interface for the keyboard and mouse. ADB would remain the Apple standard for connecting such devices until the iMac and USB in the late 1990s.
The Macintosh SE was also the first compact Mac to have the option of an internal hard drive and had an expansion slot, SE actually stands for System Expansion. The Mac SE was on sale for 3 years, by then Motorola 68000 based computers were becoming a bit outdated and Apple was moving to faster chips.
There were a number of variants. The SE FDHD (as shown below) introduced the Superdrive - basically a 3.5" floppy drive that could read 1.44MB disks. The SE/30 boasted a 68030 CPU.
The Mac SE shown below was the first Mac I ever bought, second hand from a Cash Converters! It did work fine and helped introduce me to the world of Apple in the mid-1990s. I still miss System 6 (a bit!)