Something is young if it hasn't grown up and become an adult yet. Babies and children are young. The opposite of young is old. The boy in the picture is young.
Your means something belongs to you. For example, "here is your drink". It is not the same as you're.
Yuck is a sound you make when you think something is disgusting. Children often say yuck about food they don't like to eat.
Yum, or yummy, is a sound you make when you really enjoy your food. Yummy is also an adjective that children use to describe really delicious food.
A yurt is a building made by people in Mongolia and nearby areas in central Asia. It is a round building with no central support inside, with the walls held together by tensioned rope and the walls covered by felt.