This is the 703rd most frequent German word.
stück
"Stück" = "piece" or "item"
Here, "Stück" means "piece" and is used to quantify the portion of the cake.
Ich esse ein Stück Kuchen.
I am eating a piece of cake.
In this context, "Stück" refers to a theatrical play or production.
Das Theaterstück war sehr unterhaltsam.
The play was very entertaining.
Here, "Stück" is used to indicate an individual piece or unit of wood.