holder
A person or thing that keeps or owns something.
A holder is someone or something that holds, contains, or owns something. If you slip your pencils into a pencil holder on your desk, that cup or container is doing exactly what its name suggests: holding your pencils upright and organized. A candle holder grips a candle firmly so it won't tip over. A phone holder in a car keeps your device steady while someone drives.
The word also describes ownership or possession of something official. A passport holder is someone who has been issued a passport by their country. A world record holder is the person who currently holds that record, like the fastest runner or highest jumper. When someone is a ticket holder, they possess a valid ticket to an event.
You might also encounter placeholder, which describes something temporary that saves a spot until the real thing arrives. If your teacher says “use a placeholder name for now,” she means to write something temporary that you'll replace later. A bookmark is a placeholder in a book, marking where you stopped reading.
The word fits into many combinations: stakeholder (someone with an interest in a project), shareholder (someone who owns part of a company), or cardholder (someone who owns a credit or library card). Each time, the pattern is the same: the holder has possession of something or responsibility for it.