Refers to a person actively making a selection among different options. As the event's chooser, Linda had the final say on the theme.
Pro Tip 2/3
Responsibility Hint
Implies someone has been given the responsibility to pick or decide on something. The teacher appointed Tim as the chooser of the next classroom activity.
Pro Tip 3/3
Non-technical Use
Used in everyday language, not specific to technical or computing contexts. He was the chooser of his own destiny, making decisions boldly.