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What is an enumeration (enum) in C++? What is an enum class (scoped enum) and why is it preferred? How do you assign specific values to enumerators? How do you specify the underlying type of an enum? How do you convert between an enum class and its underlying integer? Can you forward declare an enum, and what are the rules? What are the scoping and name-collision advantages of enum class? How do you implement type-safe bit flags with enum class? How can you convert an enum to a string (reflection limitations)?
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What is the difference between an enum and a set of #define constants?

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Answer

Enum enumerators are typed, scoped (for enum class), visible to the debugger, and grouped as a type, whereas #define constants are untyped preprocessor text substitutions with no scope or type safety and no debug symbol. Enums (especially enum class) are strongly preferred over #define for related constants.
enum class State { On, Off };   // typed, debuggable
// vs: #define ON 0  (untyped, no scope)
Real-world example Replacing a group of #define state constants with an enum class adds type checking and debugger names.

Common follow-ups: Why are enums safer than #define? | Do enums appear in the debugger?

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All 10 Enums & Enum Classes questions