Stand

A Stand is similar to a persona, except cooler and also not a demon. Probably.

A stand is a physical manifestation of the user's life force and a manifestation of their psyche.

King Crimson
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAA BRUNO GIVE ME THE FUCKING ARROW"

- Diavolo, King Crimson's stand user who isn't Raidou

King Crimson's abilities include stopping time, being able to erase time leaving only the results but not the in-between (Don't ask how it works, it just does), and seeing time in advance. (Or it's just whatever kind of bullshit Araki wants him to do)

Episode 7
Strange things happened on Majima and Walter (SMT) 's match, while Majima had the high hand before, these strange events turned the match around. These events included time slowing down to practically stopping, and the time between Walter beginning his Finisher and the aftermath being erased.

It's believed KC may have been summoned as a demon by an avid Devil Summoner who may have an alliance with a fellow Chaos aligned youngster. Though there's also the other possibility that it was summoned by it's stand user, Diavolo, who may be working together with Raidou to cuck Majima.

Mandom
A stand who can rewind time a certain amount of time.

Episode 9
During the Money in the Bank match, Dan Schneider had paid some wrestlers to focus on other participants (Unbeknownst to each other) so he could go and snatch the case without interference. This is believed to have lead into a cursed timeline, so Raidou used Mandom to rewind time to before the start of the match and undo the bribes by revealing the truth.

Later that night, he would need to do it again on behalf of OP as the Ref accidentally called the wrong rules on the Champion Vs Contenders match.

It is unknown how Raidou can use 2 Stands, but it is possible they are not actually "his" but merely summoning them as demons somehow.

Eat It
Reviewbrah's stand. 「Eat It」 is a semi-ethereal, incomplete torso that appears to be floating above Reviewbrah's shoulders with part of it going through the user's body phantasmagorically, with the whole user's head being submerged in it and only visible for few moments of extreme movement. The upper torso is missing a head and hands.
 * -|「Eat It」ACT1=

The only abilities shown seem to be that of punching with invisible fists; all of it's actions seemed to be synced up to Reviewbrah's, but as camera footage indicates there were several small moments of desyncing, so if the user is either unwilling of using it differently or ignores the possibility of it, is unknown. How he acquired it is also unknown.

Episode 4
Reviewbrah summoned Eat It in his match against Brad Pitt, completely outclassing him. However, the Stand showed certain signs of development: It now appeared in a pinkish color and was much more useful to Reviewbrah, hinting that his Stand development must have been a relatively recent event.
 * -|「Eat It」ACT2=

Episode 8
As of E8, Eat it is now a deep violet and started developing a head, hinting that it may be evolving into 「Beat It」. However, despite it's improvement, it stood no match against Walter (SMT)'s Devil-Summoner Samurai skills.