A stamen is the part of a flower that makes pollen. They are usually in the center of the flower, and have stalks called filaments with the pollen produced on anthers at the top of the stalks.
A stamp is a small piece of paper that is worth money. You use stamps to pay to have letters and parcels posted. Every country has their own different stamps, and lots of different designs and pictures on all their different stamp denominations.
A stampede is when a large group of animals suddenly all run in the same direction at the same time. Stampedes usually happen when something scares a herd of animals.
A star is like a big ball of fire that is very far away from us. They are thousands of times bigger than the Earth, and many stars are much, much bigger than our sun.