Supreme Leader Snoke was the dark side leader of the First Order, and The Rise of Skywalker revealed he was a creation of Emperor Palpatine rather than some mysterious ancient being. He appears in The Force Awakens and The Last Jedi, and his origin was one of the most debated mysteries of the sequel trilogy. This is what's actually confirmed.
Who he was
Snoke ran the First Order from the shadows, manipulated Ben Solo into becoming Kylo Ren, and tried to turn Rey too. He's a powerful dark side Force-user, and he looks the part: scars, a gold robe and a very large throne room.
Where he came from
For years nobody knew, so fans filled the gap with theories. The Rise of Skywalker finally answered it. Snoke was created by Palpatine, a lab-grown puppet used to steer the First Order and groom Kylo Ren from a distance. The film's companion material calls him a strandcast, basically a body built in a lab to serve a purpose, rather than a clone in the usual sense. For more on the man behind the puppet, see Emperor Palpatine's lightsaber.
Was he Darth Plagueis?
No. It was a hugely popular theory, since Palpatine's master gets mentioned in the prequels and Snoke needed a backstory. The sequels went another way, and Snoke's origin ended up tied to Palpatine instead.
How he died
Kylo Ren killed him in The Last Jedi. Snoke thought he was in control and that Kylo was about to kill Rey. Instead Kylo used the Force to turn the lightsaber toward Snoke and cut him in half, which left a lot of fans arguing about whether the character had been wasted. Kylo's own weapon is covered in Kylo Ren's lightsaber.
Any link to Grogu?
None that's confirmed. It's a fun fan theory, but nothing in canon connects Snoke to Grogu or his species.
If this made you want to look at the Sith side of things, the Sith lightsabers are a good place to browse. Was he a Sith? He's a dark side Force-user and First Order leader, with Palpatine as the real Sith power behind him.
