Show, don't tell is the maxim by which every writer operates and to which every writer aspires, even those who've attained significant success. This is because it is the heart and nature of good writing.
But, what the hell does that mean? Seems simple enough, but actually understanding, internalizing and acting on Show, don't tell requires a lot of practice and mental work just to wrap one's mind around it.
The simple chart below does a good job of laying out the difference between when you're showing as opposed to telling (found here:)
Another way to think of it is to see through the character's eyes, body and senses. For example, a character who is returning home for the death of a father after a long absence away is going to describe the house in very different terms than someone returning home after a long absence to see beloved family and friends again.