It is commonly used to refer to a set of flatware, including:
* Knives
* Forks
* Spoons
* Serving utensils
The term "argent" in French means silver, so "plat argent" literally means "flat silver".
However, "plat argent" is often used to refer to all types of flatware, not just those made of silver. It can also refer to a specific type of flatware with a silver-like finish, like stainless steel or nickel silver.