When someone selects something, they choose it from a group of things. Selects are also the things that are chosen.
If someone selects something, it is usually because they think it is the best or most suitable.
Examples:
She selects a book from the shelf.
The team captain selects the players for the game.
He selects the red apple from the basket.
The cat selects the sunny spot for a nap.
The chef selects the freshest ingredients for the dish.
The teacher selects the best student for the award.