prefix

Specifies any prefix text with which to begin Amazon S3 log object names.

You can use prefixes to organize the data that you store in Amazon S3 buckets. A prefix is a string of characters at the beginning of the object key name. A prefix can be any length, subject to the maximum length of the object key name (1,024 bytes). For more information, see Organizing objects using prefixes in the Amazon Simple Storage Service User Guide.