The Stud Riders
Each of the 37 Riders has their own unique personality and abilities. Individual attributes like Normal, Nasty, Stupid, Speedy, Vengeful, Hunter, Bluffer, Coward, Crafty, Shortsighted, Farsighted, etc., will affect the way they interact with you. The descriptions in the Riders Folder in the Single Player Menu will help you learn their strengths & weaknesses.

Bots (Computer-controlled Characters)
In terms of their 'skill', Non-Player Characters, or “Bots” have many* of the same abilities as human players. They have limited 'vision' and use line-of-sight to find cards and opponents, so Spells that affect sight and visibility will will affect them as well. They don’t 'cheat'. They don’t know where the “good cards” are any more than you do. They are familiar with the terrain, however, and they’re smart enough to Bluff, Fold, and target Jokers and other Items when they need them... so don’t underestimate them! Select the “Difficulty Level” that’s right for you.

*Oddly, most of them refuse to use Spells ...something about fear of "The Ancient Damp Ones".)