What it is: A file stored in S3, plus metadata, stored under a key (path-like name).

What it’s for:

• Store and retrieve files using the object key.
• Attach metadata (content-type, tags, custom metadata).

Key ideas:

• Object identity = bucket + key.
• S3 is not a real “folder” system—folders are part of the key naming.
• You can set permissions via ACLs (less preferred) or policies.

Exam cues:

• “S3 folder isn’t real” → it’s a prefix in object keys.

Hard words:

• *metadata* /ˈmetəˌdeɪtə/: siêu dữ liệu
• *prefix* /ˈpriːfɪks/: tiền tố
• *content-type* /ˈkɑːntent taɪp/: loại nội dung (MIME type)