Type erasure is the compiler mechanism that removes generic type information after compile-time checking, replacing type parameters with their bound (or Object) in the compiled bytecode. This is why generic type information isn't available at runtime and why you can't do things like `new T()` or `list instanceof List<String>`.

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#Type Erasure#Generics Internals

Why Erasure Exists

Generics were added in Java 5 while preserving backward compatibility with pre-generics bytecode and libraries. Erasing generic type parameters to their raw form at compile time let the JVM itself remain unchanged, at the cost of type information not being available via reflection at runtime.

Source: List<String> → Compiler checks types → Type Erasure → Bytecode: List (raw, casts inserted automatically)

Interview Answer

Type erasure means the compiler enforces generic type safety only at compile time, then strips the type parameters and inserts the necessary casts into the bytecode — at runtime, List and List are literally the same class, `List`. This is why you can't check `instanceof List` or create `new T()` directly.