Solid-state amp with 50W Celestion speaker, I bought it in the '80s. It is powerful enough, even for rehearsals with a band. Onstage, I think miking through the PA is indispensable.
2 channels: The first ones is clean, nice, but not comprehensive enough (volume, bass and treble), as for the second channel, it's a "Boost" with more possibilities (Gain, volume, treble, middle, bass). Plus a Master section to adjust the overall volume and the reverb for the two channels.
An all-plastic pedal to toggle between the clean and the distorted sound (overdrive, at least), and it also allows you to activate the reverb.
Spring reverb.

UTILIZATION

Yes, it's easy to use, except for the loads of jacks on the rear, because they are not labeled (yes, the first one on the right is to plug the footswitch) => The user's manual can be downloaded here: http://www.drtube.com/schematics/marshall/jcm800-sc-manual.pdf, and it makes everything easier!
However, the sound is very good, the clean channel has a good dynamic response and the second channel has a nice overdrive. You can tell the brand's touch, even if it's a solid-state amp.
The pots have a tendency to crackle a bit, like on all old amps.
I got no manual although I bought it new!

SOUNDS

I'm using it again now because some time ago I opted for a software Guitar Rig-type solution, which offers a wider array of sound possibilities, but finally, nothing can replace a real amp. Very '70/'80s pop/rock and even hard rock (which is normal given its age!). The sound is not modern at all, but rather "vintage."
It's perfect for a Fender Strat or a Gibson Les Paul.

OVERALL OPINION

Excellent entry-level amp back then. I found it secondhand online for a very decent price. But do be careful with the crackling pots, although I think it's something pretty common to all Marshalls!