"Denim" and "jeans" are closely related but refer to different things. Denim is a sturdy cotton fabric that's typically blue and has a twill weave, while jeans are a type of trousers made from denim. So, all jeans are made from denim, but not all denim is turned into jeans.
Think of it this way: denim is the versatile material, and jeans are the creative canvas created from that material! They both have a special place in fashion, inspiring unique and stylish outfits.