Plain Bearings

A plain bearing is the simplest type of bearing. It is essentially just a smooth surface that allows one part to slide or rotate against another part without using rolling elements like balls or rollers.
Here is the simple breakdown:
• No Moving Parts (Besides the Shaft): It’s just a smooth, usually circular, surface or sleeve that a shaft slides into.
• Relies on Lubrication: It needs oil or grease (or sometimes it's self-lubricating material like plastic or bronze) to create a slippery film between the moving shaft and the stationary housing. Without lubricant, the parts would grind and quickly wear out.
• Simple and Cheap: They are inexpensive, compact, and used in countless everyday machines, from door hinges and car engines to household appliances and simple gears.
• Also Called Bushings: These are very commonly referred to as "bushings."
In short, a plain bearing is a simple, smooth sleeve or pad where one machine part slides against another with the help of lubricant to prevent grinding.