Enum
In plain terms
A type with a fixed set of named constant values.
Going deeper
An enum (enumeration) defines a type whose values are a fixed list of named options, improving clarity and safety over raw constants. It enumerates valid choices.
Under the hood
Prevents invalid values and enables exhaustive checks; some languages allow methods on enums.
Examples
Color {RED, GREEN, BLUE}, status codes, days of week, type safety.
Think of it like...
Like a multiple-choice field that only accepts the listed options.